Optical system, illumination system, display system, and moving vehicle

ABSTRACT

An optical system includes a light guide member and a prism. The light guide member has: an incident surface on which light is incident; and a first surface and a second surface facing each other. The second surface is a light emergent surface. The prism is provided for the first surface and reflects, toward the second surface, the light passing inside the light guide member. The light guide member includes a direct optical path, along which the light that has entered the light guide member through the incident surface is directly reflected from the prism and allowed to emerge from the second surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Bypass Continuation of InternationalApplication No. PCT/JP2020/017389 filed on Apr. 22, 2020, which is basedupon, and claims the benefit of priority to, Japanese Patent ApplicationNo. 2019-086747 filed on Apr. 26, 2019, Japanese Patent Application No.2019-146730 filed on Aug. 8, 2019, Japanese Patent Application No.2019-146731 filed on Aug. 8, 2019, Japanese Patent Application No.2019-146732 filed on Aug. 8, 2019, and Japanese Patent Application No.2019-146733 filed on Aug. 8, 2019. The entire contents of bothapplications are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure generally relates to an optical system, anillumination system, a display system, and a moving vehicle. Moreparticularly, the present disclosure relates to an optical systemconfigured to control light which has been incident through an incidentsurface to make the light emerge from an emergent surface, anillumination system, a display system, and a moving vehicle.

BACKGROUND ART

JP 2017-142491 A discloses an image display device (display system) forprojecting a virtual image onto a target space. This image displaydevice is a head-up display (HUD) device for automobiles. Projectedlight, emerging as image light from the HUD device (optical system)provided in a dashboard of an automobile, is reflected from thewindshield thereof toward a driver who is a viewer. This allows the user(driver) to view an image such as a navigation image as a virtual imageas if the virtual image is superimposed on a view of the background suchas a road surface.

SUMMARY

The present disclosure provides an optical system, an illuminationsystem, a display system, and a moving vehicle, all of which areconfigured to contribute to increasing the light extraction efficiency.

An optical system according to an aspect of the present disclosureincludes a light guide member and a prism. The light guide member has:an incident surface on which light is incident; and a first surface anda second surface facing each other. The second surface is a lightemergent surface. The prism is provided for the first surface andreflects, toward the second surface, the light passing inside the lightguide member. The light guide member includes a direct optical path,along which the light that has entered the light guide member throughthe incident surface is directly reflected from the prism and allowed toemerge from the second surface.

An illumination system according to another aspect of the presentdisclosure includes the optical system described above and a lightsource. The light source emits light toward the incident surface throughthe light control member.

A display system according to still another aspect of the presentdisclosure includes the illumination system described above and adisplay. The display receives the light emerging from the illuminationsystem and displays an image thereon.

A moving vehicle according to yet another aspect of the presentdisclosure includes the display system described above and a movingvehicle body to be equipped with the display system.

BRIEF DESCRIPTION OF DRAWINGS

The figures depict one or more implementations in accordance with thepresent teaching, by way of example only, not by way of limitations. Inthe figures, like reference numerals refer to the same or similarelements.

FIGS. 1A and 1B are cross-sectional views indicating an outline of anoptical system according to a first embodiment of the presentdisclosure;

FIG. 2 is a plan view indicating an outline of the optical system;

FIGS. 3A and 3B show optical paths in the optical system;

FIG. 4 illustrates a moving vehicle including a display system that usesthe optical system;

FIG. 5 illustrates the display system;

FIGS. 6A and 6B are cross-sectional views indicating an outline of anoptical system according to a comparative example;

FIGS. 7A-7C indicate an outline of optical systems according to a firstvariation of the first embodiment of the present disclosure;

FIGS. 8A and 8B are cross-sectional views indicating an outline of anoptical system according to a second variation of the first embodimentof the present disclosure;

FIG. 9 is a cross-sectional view indicating an outline of an opticalsystem according to a third variation of the first embodiment of thepresent disclosure;

FIG. 10A is a cross-sectional view indicating an outline of an opticalsystem according to a second embodiment;

FIG. 10B is a schematic representation illustrating, on a larger scale,the region A1 shown in FIG. 10A;

FIG. 11 is a schematic representation indicating an outline of a lightcontrol member of the optical system;

FIG. 12 is a perspective view indicating an outline of the opticalsystem;

FIG. 13 illustrates a display system that uses the optical system;

FIG. 14 illustrates a moving vehicle including the display system;

FIG. 15A is a plan view of the optical system;

FIG. 15B is a front view of the optical system;

FIG. 15C is a bottom view of the optical system;

FIG. 15D is a side view of the optical system;

FIG. 16A is a schematic representation illustrating, on a larger scale,the region A1 shown in FIG. 15C

FIG. 16B is a cross-sectional view thereof taken along the plane B1-B1shown in FIG. 16A;

FIG. 17A is a perspective view illustrating the shape of the lightcontrol member;

FIG. 17B is a cross-sectional view thereof taken along the plane B1-B1shown in FIG. 17A;

FIG. 17C is a cross-sectional view thereof taken along the plane C1-C1shown in FIG. 17A;

FIG. 18A illustrates a light intensity distribution of the light controlmember;

FIG. 18B illustrates a light intensity distribution of a light controlmember according to a comparative example;

FIG. 19A illustrates a light intensity distribution of the light controlmember;

FIG. 19B illustrates a light intensity distribution of a light controlmember according to a comparative example;

FIG. 20A illustrates a light intensity distribution in a light guidemember as viewed from one end along its thickness in a situation wherelight is directed from the light control member toward a light guidemember;

FIG. 20B illustrates a light intensity distribution in a light guidemember as viewed from one end along its thickness in a situation wherelight is directed from a light control member according to a comparativeexample toward a light guide member;

FIG. 21A schematically illustrates light rays passing inside the lightcontrol member;

FIG. 21B schematically illustrates light rays passing inside a lightcontrol member according to a comparative example;

FIG. 21C schematically illustrates light rays passing inside a lightcontrol member according to another comparative example;

FIG. 22A is a side view indicating an outline of an optical systemaccording to a first variation of a second embodiment;

FIG. 22B is a schematic representation illustrating, on a larger scale,the region A1 shown in FIG. 22A;

FIG. 22C is a schematic representation illustrating, on a larger scale,the region A2 shown in FIG. 22A;

FIG. 23A is a side view indicating an outline of an optical systemaccording to a second variation of the second embodiment;

FIG. 23B is a cross-sectional view indicating the outline of the opticalsystem;

FIG. 24 is a front view indicating an outline of a light control memberaccording to a third variation of the second embodiment;

FIG. 25A illustrates an illumination system that uses an optical systemaccording to a fourth variation of the second embodiment;

FIG. 25B is a schematic representation illustrating, on a larger scale,the region A1 shown in FIG. 25A;

FIG. 26A is a plan view of a main part illustrating an exemplary opticalsystem according to a fifth variation of the second embodiment;

FIG. 26B is a plan view of a main part illustrating another exemplaryoptical system according to the fifth variation;

FIG. 27A is a schematic representation illustrating an exemplary prismaccording to a sixth variation of the second embodiment;

FIG. 27B is a schematic representation illustrating another exemplaryprism according to the sixth variation;

FIG. 28A is a schematic representation illustrating still anotherexemplary prism according to the sixth variation;

FIG. 28B is a schematic representation illustrating yet anotherexemplary prism according to the sixth variation;

FIG. 29A is a schematic representation illustrating yet anotherexemplary prism according to the sixth variation;

FIG. 29B is a schematic representation illustrating yet anotherexemplary prism according to the sixth variation;

FIG. 30A is a schematic representation illustrating an exemplary prismaccording to a seventh variation of the second embodiment;

FIG. 30B is a schematic representation illustrating another exemplaryprism according to the seventh variation;

FIG. 30C is a schematic representation illustrating still anotherexemplary prism according to the seventh variation;

FIG. 31A is a bottom view indicating an outline of an optical systemaccording to a third embodiment;

FIG. 31B is a schematic representation illustrating, on a larger scale,a first zone of the optical system;

FIG. 31C is a schematic representation illustrating, on a larger scale,a hybrid zone of the optical system; and

FIG. 31D is a schematic representation illustrating, on a larger scale,a second zone of the optical system.

DETAILED DESCRIPTION First Embodiment

(1) Overview

An optical system 100 (see FIGS. 1A and 1B) according to an exemplaryembodiment has the capability of controlling light incident through anincident surface 10 and allowing the light to emerge from an emergentsurface (second surface 12). The optical system 100 includes a lightguide member 1, a light control member 2, and a prism 3 as shown inFIG. 1. The optical system 100 forms, along with a light source 4, anillumination system 200. In other words, the illumination system 200includes the optical system 100 and the light source 4. The light source4 emits light toward the incident surface 10 through the light controlmember 2.

The light guide member 1 has the incident surface 10 on which the lightis incident and a first surface 11 and the second surface 12 facing eachother. The second surface 12 is a light emergent surface. The lightguide member 1 is a so-called “light guide plate.” In this embodiment,the light guide member 1 has the shape of a flat plate and the twosurfaces thereof facing each other along the thickness of the lightguide member 1 are the first surface 11 and the second surface 12. Also,one of the four side surfaces of the light guide member 1 is theincident surface 10. That is to say, the light guide member 1 isconfigured such that when light is incident through a side surfaceserving as the incident surface 10, the second surface 12 serving as theemergent surface provides surface-emitting light.

The light control member 2 condenses the light traveling toward theincident surface 10 and directs the condensed light toward the incidentsurface 10. In this embodiment, the light emitted from the light source4 is incident on the incident surface 10 of the light guide member 1through the light control member 2. Then, the light that has entered thelight control member 2 is controlled to have its divergence anglenarrowed and be directed toward the incident surface 10. In thisembodiment, the light control member 2 controls the divergence angle ofthe light that has entered the light control member 2 such that theoptical path of the light directed toward the incident surface 10becomes as close as possible to an optical path parallel to the secondsurface 12.

The prism 3 is provided for the first surface 11 and reflects, towardthe second surface 12, the light passing inside the light guide member1. In this embodiment, a plurality of prisms 3 are provided for thefirst surface 11. Each of the prisms 3 is configured to totally reflectthe light incident thereon. Naturally, the prism 3 does not have to beconfigured to totally reflect the incident light entirely.Alternatively, in another implementation, part of the incident light isnot totally reflected but may pass through the inside of the prism 3.

In the light guide member 1, most of the light that has entered thelight guide member 1 through the incident surface 10 is reflected fromthe prisms 3, without being reflected from the rest of the first surface11 or the second surface 12 other than the prisms 3, before emergingfrom the second surface 12. That is to say, the light guide member 1includes a direct optical path L1, along which the light that hasentered the light guide member 1 through the incident surface 10 isdirectly reflected from the prisms 3 and allowed to emerge from thesecond surface 12 (see FIG. 3B).

As can be seen, according to this embodiment, the light, which has hadits divergence angle controlled through the light control member 2, isdirectly reflected from the prisms 3 provided for the first surface 11of the light guide member 1 and then allowed to emerge from the secondsurface 12. Thus, this embodiment achieves the advantage of contributingto increasing the light extraction efficiency, compared to animplementation in which the incident light is repeatedly totallyreflected from the first surface 11 and the second surface 12 of thelight guide member 1 before emerging from the second surface 12. As usedherein, the “extraction efficiency” refers to the proportion of thequantity of the light emerging from the second surface 12 (emergentsurface) of the light guide member 1 with respect to the quantity of thelight incident on the incident surface 10 of the light guide member 1.

(2) Details

An optical system 100 according to this embodiment and a display system300 that uses the optical system 100 will be described.

(2.1) Display System

First, the display system 300 will be described. The display system 300may be used in, for example, a head-up display to be installed in anautomobile (moving vehicle) B1 to present, within the user's U1 sight,various types of driver assistance information including velocityinformation, condition information, and driving-related informationabout the automobile B1. Examples of the driving-related informationabout the automobile B1 include navigation-related informationpresenting proposed traveling routes and adaptive cruise control (ACC)related information for use to keep the traveling velocity and thedistance between the vehicles constant.

As shown in FIGS. 4 and 5, the display system 300 includes an imagedisplay unit 310, an optical system 320, and a control unit 330. Thedisplay system 300 further includes a housing 340 for housing the imagedisplay unit 310, the optical system 320, and the control unit 330therein.

The display system 300 is installed in the moving vehicle body B11 ofthe automobile B1 as an exemplary moving vehicle. That is to say, themoving vehicle (automobile) B1 includes the display system 300 and themoving vehicle body B11 in which the display system 300 is installed.

The housing 340 may be a molded product of a synthetic resin, forexample. In the housing 340, housed are the image display unit 310, theoptical system 320, the control unit 330, and other members. The housing340 is installed in a dashboard B13 of the moving vehicle body B11. Thelight beam reflected from a second mirror 322 (to be described later) ofthe optical system 320 passes through an opening provided through theupper surface of the housing 340 to emerge toward a reflective member(windshield B12). Then, the light beam is reflected from the windshieldB12 and condensed into an eye box C1. The reflective member may beimplemented as, for example, a combiner provided for the moving vehiclebody B11.

The image display unit 310 includes a display device 311 and a lensarray 312 arranged on a display screen 313 of the display device 311.The image display unit 310 has the capability of displaying astereoscopic image by the light field method, according to which anobject in an image captured is made to look stereoscopic by reproducinglight beams emerging from the object in a plurality of directions.

The display device 311 is housed in the housing 340 such that thedisplay screen 314 faces a first mirror 321 (to be described later). Thedisplay screen 314 of the display device 311 has a shape (e.g., arectangular shape) corresponding to the range of the image to beprojected toward the user U1 (i.e., the shape of the windshield B12). Onthe display screen 314 of the display device 311, a plurality of pixelsare arranged to form an array. The plurality of pixels of the displaydevice 311 emits light beams under the control of the control unit 330.As a result, an image to be displayed on the display screen 314 isformed by the light beams emerging from the display screen 314 of thedisplay device 311. The display device 311 may be implemented as anillumination system 200 including a display 5 and an optical system 100.The display 5 may be implemented as, for example, a liquid crystaldisplay or an organic electroluminescent (OEL) display, for example, anddisplays an image thereon on receiving the light emerging from theillumination system 200. That is to say, it can be said that the displaysystem 300 includes the illumination system 200 and the display 5.

On the display screen 314 of the display device 311, arranged is thelens array 312. In this case, the surface of the lens array 312constitutes the display screen 313 of the image display unit 310. Thelens array 312 includes a plurality of lenses which are arranged to forman array.

The image displayed on the display screen 314 of the display device 311is viewed by the user U1 who has a viewpoint inside the eye box C1through the lens array 312 and the optical system 320. This allows theuser U1 to view a virtual image E1 superimposed along the travelingsurface D1 of the automobile B1 and a virtual image renderedstereoscopically along a plane PL1 perpendicular to the travelingsurface D1.

Note that the light field method is not the only method allowing theimage display unit 310 to display the virtual image of the stereoscopicrendering target stereoscopically. Alternatively, the image display unit310 may also adopt a parallax method, which allows the user U1 to view avirtual image of the stereoscopic rendering target by projecting a pairof images with a parallax onto the user's U1 right and left eyes,respectively.

The optical system 320 condenses the light emerging from the displayscreen 313 of the image display unit 310 into the eye box C1. In thisembodiment, the optical system 320 includes: the first mirror 321, whichmay be a convex mirror, for example; the second mirror 322, which may bea concave mirror; and the windshield B12.

The first mirror 321 reflects the light emerging from the image displayunit 310 to make the light incident on the second mirror 322. The secondmirror 322 reflects the light, which has been incident thereon from thefirst mirror 321, toward the windshield B12. The windshield B12 reflectsthe light, which has been incident thereon from the second mirror 322,to make the light incident into the eye box C1.

The control unit 330 includes a computer system, for example. Thecomputer system may include one or more processors and one or morememories as principal hardware components. The functions of the controlunit 330 (e.g., the functions of the rendering control unit 331, theimage data producing unit 332, and the output unit 333) may be performedby making the one or more processors execute a program stored in the oneor more memories or the storage unit 334 of the computer system. Theprogram may be stored in advance in the one or more memories or thestorage unit 334 of the computer system. Alternatively, the program mayalso be downloaded through a telecommunications line or be distributedafter having been recorded in some non-transitory storage medium such asa memory card, an optical disc, or a hard disk drive, any of which isreadable for the computer system.

The storage unit 334 may be implemented as, for example, anon-transitory storage medium such as a programmable nonvolatilesemiconductor memory. The storage unit 334 stores a program to beexecuted by the control unit 330 and other data. In addition, thedisplay system 300 according to this embodiment is used to present,within the user's U1 sight, driver assistance information includingvelocity information, condition information, and driving informationabout the automobile B1 as described above. Thus, the type of thevirtual images displayed by the display system 300 are determined inadvance. The image data to display the virtual images (including avirtual image E1 as a plane rendering target and a virtual image as astereoscopic rendering target) is stored in advance in the storage unit334.

The rendering control unit 331 receives detection signals from varioussensors 350 installed in the automobile B1. The sensors 350 may besensors for detecting various types of information for use in anadvanced driver assistance system (ADAS), for example. The sensors 350include at least one sensor selected from the group consisting of:sensors for measuring the velocity, temperature, and residual fuel ofthe automobile B1; an image sensor for shooting video presenting thesurroundings of the automobile B1; and a milli-wave radar and a lightdetection and ranging (LiDAR) sensor for detecting objects presentaround the automobile B1.

The rendering control unit 331 retrieves, in accordance with thedetection signals supplied from the sensors 350, a single or multipleitems of image data for displaying information about the detectionsignals from the storage unit 334. In this case, when multiple types ofinformation are displayed on the image display unit 310, the renderingcontrol unit 331 acquires multiple items of image data for displayingthe multiple types of information. In addition, the rendering controlunit 331 also obtains, in accordance with the detection signals suppliedfrom the sensors 350, location information about the display location ofthe virtual image in a target space where the virtual image isdisplayed. Then, the rendering control unit 331 outputs the image dataof the virtual image(s) to display and the location information to theimage data producing unit 332.

The image data producing unit 332 produces, based on the image data andlocation information provided by the rendering control unit 331, imagedata for displaying the virtual image(s) to display.

The output unit 333 outputs the image data that has been produced by theimage data producing unit 332 to the display device 311 to have an imagebased on the image data displayed on the display screen 314 of thedisplay device 311. The light representing the image displayed on thedisplay screen 314 is condensed into the eye box C1 through the lensarray 312 and the optical system 320, thus making the user U1 view thevirtual image.

(2.2) Optical system

Next, the optical system 100 will be described with reference to FIGS.1A-3B. The optical system 100 includes a light guide member 1, aplurality of light control members 2, and a plurality of prisms 3. Theoptical system 100 forms, along with a plurality of light sources 4, theillumination system 200. In the following description, a width directiondefined with respect to the light guide member 1 (i.e., a direction inwhich the plurality of light sources 4 are arranged side by side in FIG.2) will be hereinafter referred to as an “X direction” and a depthdirection defined with respect to the light guide member 1 (i.e., adirection in which the plurality of prisms 3 are arranged side by sidein FIG. 1A) will be hereinafter referred to as a “Y direction.”Furthermore, in the following description, a thickness direction definedwith respect to the light guide member 1 (i.e., a direction in which thefirst surface 11 and the second surface 12 are arranged one on top ofthe other in FIG. 1A) will be hereinafter referred to as a “Zdirection.”

Note that the arrows indicating the “X direction,” “Y direction,” and “Zdirection” on the drawings are shown there just as an assistant todescription and are insubstantial ones. Also, the dotted arrows shown onthe drawings conceptually indicate an optical path of the light emittedfrom any of the light sources 4 and passing inside the light guidemember 1.

The light sources 4 are each implemented as a solid-state light-emittingelement such as a light-emitting diode (LED) or an organicelectroluminescent (OEL) element. The plurality of light sources 4 arearranged to be spaced from each other in the X direction and to face theincident surface 10 of the light guide member 1 as shown in FIG. 2. Eachof the plurality of light sources 4 is provided one to one for anassociated one of the plurality of light control members 2 provided onthe incident surface 10 of the light guide member 1.

The light guide member 1 is made of a material having alight-transmitting property such as an acrylic resin and has a flatplate shape. Of two side surfaces, facing each other in the Y direction,of the light guide member 1, one side surface (i.e., the left sidesurface shown in FIG. 1A) is the incident surface 10 on which the lightbeams emitted from the plurality of light sources 4 are incident throughthe plurality of light control members 2. The two surfaces, facing eachother in the Z direction, of the light guide member 1 are the firstsurface 11 and the second surface 12, respectively. The first surface 11corresponds to the lower surface shown in FIG. 1A and the second surface12 corresponds to the upper surface shown in FIG. 1A. The second surface12 is an emergent surface, from which the light passing inside the lightguide member 1 emerges out of the light guide member 1.

In this embodiment, the second surface 12 is surface perpendicular tothe incident surface 10, i.e., a surface parallel to an XY plane. On theother hand, the first surface 11 is a surface which is not perpendicularto the incident surface 10 but is tilted with respect to the XY plane.Specifically, the first surface 11 is tilted such that as the distancefrom the incident surface 10 increases, the first surface 11 comescloser toward the second surface 12. That is to say, in this embodiment,the first surface 11 and the second surface 12 are tilted with respectto each other.

Each of the light control members 2 may be configured as, for example, acollimator lens which condenses the light traveling toward the incidentsurface 10 and directs the condensed light toward the incident surface10. Specifically, each light control member 2 has a refractive surface20 and a totally reflective surface 21 as shown in FIG. 3A. Therefractive surface 20 refracts a part of the light emitted from thelight source 4 and directs the refracted light toward the incidentsurface 10. The totally reflective surface 21 totally reflects a part ofthe light emitted from the light source 4 and directs the totallyreflected light toward the incident surface 10. In this manner, thelight control member 2 controls the light emitted from the light source4 to narrow its divergence angle by refracting part or all of the lightemitted from the light source 4. Thus, the light control member 2controls the divergence angle of the light emitted from the light source4 such that the optical path of the light going out of the light controlmember 2 is as close as possible to an optical path perpendicular to theincident surface 10, i.e., an optical path parallel to the secondsurface 12.

In this embodiment, the plurality of light control members 2 arearranged in the X direction at an end portion, forming the incidentsurface 10, of the light guide member 1 as shown in FIG. 2. That is tosay, in this embodiment, the light control members 2 are integrated withthe light guide member 1. In addition, the plurality of light controlmembers 2 correspond one to one to the plurality of light sources 4 asdescribed above. Thus, each of the plurality of light control members 2controls the divergence angle of the light emitted from an associatedone of the light sources 4 and directs the light toward the incidentsurface 10.

The prism 3 is formed on the first surface 11 by patterning an endportion, forming the first surface 11, of the light guide member 1 suchthat its cross section as viewed in the X direction forms a triangularrecess. The prism 3 has a reflective surface 30 for reflecting, towardthe second surface 12, the light that has been incident thereon bypassing inside the light guide member 1 as shown in FIG. 1B. Note thatFIG. 1B is an enlarged view of the portion encircled with a one-dotchain circle in FIG. 1A.

The angle θ1 formed between the reflective surface 30 and the firstsurface 11 (i.e., the tilt angle of the reflective surface 30) isdefined such that the angle of incidence θ0 of the light incident on thereflective surface 30 becomes equal to or greater than a critical angle.That is to say, the reflective surface 30 is tilted with respect to thefirst surface 11 to totally reflect the incident light. In addition, thetilt angle θ1 of the reflective surface 30 is set such that the lighttotally reflected from the reflective surface 30 travels in a directionincluding a direction that is substantially perpendicular to the secondsurface 12. In this case, the angles of incidence θ0 of the lightincident on the plurality of prisms 3 vary from one prism 3 to another.

In this embodiment, each of the plurality of prisms 3 is formed toextend linearly parallel to the X direction when viewed in plan in the Zdirection as shown in FIG. 2. In addition, the plurality of prisms 3 arearranged on the end portion, forming the first surface 11, of the lightguide member 1 to be spaced from each other in the Y direction. That isto say, in this embodiment, the plurality of prisms 3 are provided to bearranged side by side in the direction in which the light is incident onthe incident surface 10 (i.e., in the Y direction). Specifically, theplurality of prisms 3 are provided to be spaced from each other in the Ydirection such that the light traveling toward the first surface 11 bypassing inside the light guide member 1 is reflected from any one of theplurality of prisms 3.

Next, the light emission principle of the optical system 100 accordingto this embodiment will be described with reference to FIGS. 3A and 3B.First, as shown in FIG. 3A, the light emitted from each light source 4has its divergence angle controlled by passing through an associatedlight control member 2. Then, the light with the divergence angle thuscontrolled is directed from the light control member 2 toward theincident surface 10 of the light guide member 1. The optical path of thelight directed from the light control member 2 becomes an optical pathsubstantially perpendicular to the incident surface 10, i.e., an opticalpath substantially parallel to the second surface 12. In addition, thefirst surface 11 is tilted such that as the distance from the incidentsurface 10 increases, the first surface 11 comes closer toward thesecond surface 12. As a result, most of the light incident on theincident surface 10 reaches the first surface 11 without reaching thesecond surface 12 or a side surface 13, facing the incident surface 10,of the light guide member 1.

In addition, most of the light incident on the incident surface 10 istotally reflected from the reflective surface 30 of any of the pluralityof prisms 3 on the first surface 11 without being reflected from thefirst surface 11 or the second surface 12 as shown in FIG. 3B. That isto say, the light guide member 1 includes a direct optical path L1,along which the light that has entered the light guide member 1 throughthe incident surface 10 is directly reflected from any of the prisms 3and allowed to emerge from the second surface 12. Furthermore, in thisembodiment, the direct optical path L1 includes the optical path of thelight totally reflected from any of the prisms 3. The light totallyreflected from the reflective surface 30 of each of the prism 3 travelsalong an optical path which is substantially perpendicular to the secondsurface 12 and emerges from the second surface 12. This causes the lightemitted to be transmitted through the entire second surface 12 (i.e.,allows the entire second surface 12 to provide surface-emitting light).

In this case, part of the light incident through the incident surface 10is directed toward the second surface 12 without traveling toward thefirst surface 11 or the side surface 13. The light directed toward thesecond surface 12 may be totally reflected from the second surface 12.Then, the light totally reflected from the second surface 12 is directedtoward the first surface 11, and therefore, totally reflected from thereflective surface 30 of any of the plurality of prisms 3. The lighttotally reflected from the reflective surface 30 of the prism 3, as wellas the light traveling along the direct optical path L1, travels alongan optical path substantially perpendicular to the second surface 12 andemerges from the second surface 12. That is to say, the light guidemember 1 may further include an indirect optical path L2, along whichthe light that has entered the light guide member 1 through the incidentsurface 10 is once reflected from the second surface 12, reflected againfrom any of the prisms 3, and then allowed to emerge from the secondsurface 12.

Next, an advantage to be achieved by the optical system 100 according tothis embodiment will be described in comparison with an optical system400 according to a comparative example. As shown in FIGS. 6A and 6B, theoptical system 400 according to the comparative example includes neitherthe plurality of light control members 2 nor the plurality of prisms 3,which is a major difference from the optical system 100 according tothis embodiment. In addition, in the optical system 400 according to thecomparative example, a first surface 501 is tilted with respect to asecond surface 502 such that the light incident on the first surface 501of the light guide plate 401 is totally reflected, which is anothermajor difference from the optical system 100 according to thisembodiment.

In the optical system 400 according to the comparative example, thelight emitted from a light source 402 is incident on an incident surface500 of the light guide plate 401 without having its divergence anglecontrolled. Thus, the optical system 400 according to the comparativeexample almost evenly splits the light incident on the incident surface500 into light traveling toward the first surface 501 and lighttraveling toward the second surface 502. Then, in the optical system 400according to the comparative example, the light incident on the incidentsurface 500 is repeatedly totally reflected from the first surface 501and the second surface 502 before emerging from the second surface 502as in a general light guide plate. Thus, the optical system 400according to the comparative example allows the entire second surface502 to provide surface-emitting light.

However, the optical system 400 according to the comparative example isdesigned to allow the entire second surface 502 to providesurface-emitting light by having the incident light repeatedly totallyreflected from the first surface 501 and the second surface 502 of thelight guide plate 401. Thus, the larger the number of times the light istotally reflected, the more likely the condition for the totalreflection (i.e., angle of incidence≥critical angle) fails to besatisfied, thus increasing the chances of the light leaking through thefirst surface 501.

Particularly when applied to a head-up display installed in anautomobile B1 as in the display system 300 according to this embodiment,the optical system is required to achieve a narrower viewing angle and ahigher light intensity than a general optical system including a lightguide plate. To narrow the viewing angle, the emergent surface of thelight guide plate needs to have a decreased area (i.e., the light guideplate needs to be downsized). However, the smaller the light guide plateis, the shorter the distance that the light incident on the light guideplate may reach (hereinafter referred to as a “light guide distance”)is. The shorter the light guide distance is, the larger the proportionof the light leaking through a side surface facing the incident surfacewithout emerging from the emergent surface of the light guide memberbecomes. This makes it increasing difficult to ensure a sufficient lightintensity (in other words, to ensure a sufficient light extractionefficiency).

Thus, to ensure a sufficient light intensity even with a light guidemember having a short light guide distance, the first surface 501 of thelight guide plate 401 may be tilted with respect to the second surface502 thereof as in the optical system 400 according to the comparativeexample. However, as described above, the optical system 400 accordingto the comparative example also allows the light to leak through thefirst surface 501 easily. Consequently, it is also difficult even forthe optical system 400 according to the comparative example to ensure asufficient light extraction efficiency.

In contrast, the optical system 100 according to this embodimentincludes the light control members 2 and the prisms 3 as describedabove, and therefore, allows most of the light that has entered thelight guide member 1 through the incident surface 10 to travel along thedirect optical path L1. That is to say, according to this embodiment,most of the light that has entered the light guide member 1 through theincident surface 10 is directly incident on any of the prisms 3 andallowed to emerge from the second surface 12 without being repeatedlytotally reflected from the first surface 11 and the second surface 12.Therefore, according to this embodiment, the condition for the totalreflection rarely fails be satisfied, unlike the optical system 400according to the comparative example. This reduces the chances of thelight leaking out through the first surface 11 and eventuallycontributes to increasing the light extraction efficiency.

Note that part of the light that has entered the light guide member 1through incident surface 10 travels along the indirect optical path L2.Even in that case, the incident light is totally reflected only oncefrom the second surface 12 before reaching any of the prisms 3, thusreducing the chances of the condition for the total reflection failingto be satisfied and allowing the light to leak out through the firstsurface 11 much less often, compared to the optical system 400 accordingto the comparative example.

As can be seen, the optical system 100 according to this embodiment isdesigned to minimize the number of times the light passing inside thelight guide member 1 is totally reflected, and therefore, contributes toincreasing the light extraction efficiency more effectively, compared tothe optical system 400 according to the comparative example.

In addition, according to this embodiment, the first surface 11 and thesecond surface 12 are tilted with respect to each other. Thus, accordingto this embodiment, the light control members 2 need to narrow thedivergence angle of the light incident on the incident surface 10 to alesser degree than in a situation where the first surface 11 and thesecond surface 12 are parallel to each other. Consequently, unlike thesituation where the first surface 11 and the second surface 12 areparallel to each other, there is no need according to this embodiment toincrease the distance between each of the light control members 2 and anassociated one of the light sources 4, thus achieving the advantage ofcontributing more effectively to downsizing the illumination system 200.

(3) Variations

Note that the embodiment described above is only an exemplary one ofvarious embodiments of the present disclosure and should not beconstrued as limiting. Rather, the exemplary embodiment may be readilymodified in various manners depending on a design choice or any otherfactor without departing from the scope of the present disclosure. Thedrawings referred to in the foregoing description of embodiments are allschematic representations. That is to say, the ratio of the dimensions(including thicknesses) of respective constituent elements illustratedon the drawings does not always reflect their actual dimensional ratio.

Next, variations of the exemplary embodiment will be enumerated oneafter another. Note that any the variations to be described below may beadopted as appropriate in combination with the exemplary embodimentdescribed above.

(3.1) First Variation

In an optical system 100A according to a first variation, each prism 3is divided into a plurality of (e.g., three in this variation) smallprisms 31 as shown in FIG. 7A, which is a major difference from theoptical system 100 according to the exemplary embodiment describedabove. That is to say, according to this variation, each prism 3includes a plurality of small prisms 31, which are divided to be spacedapart from each other. Note that in FIG. 7A, only one of a plurality ofprisms 3 which are arranged in the Y direction is shown. Also, in FIG.7A, only a part, facing a single light source 4 and a single lightcontrol member 2, of the single prism 3 is shown.

The plurality of small prisms 31 are arranged side by side to draw anarc-shaped curve when viewed in the Z direction. That is to say,according to this embodiment, at least part of each prism 3 (i.e., thesmall prisms 31) is tilted with respect to the incident surface 10 whenviewed in the direction in which the first surface 11 and the secondsurface 12 are arranged one on top of the other (in the Z direction). Inaddition, according to this variation, two or more of the plurality ofsmall prisms 31 are arranged to form a curved pattern when viewed in thedirection in which the first surface 11 and the second surface 12 arearranged one on top of the other (in the Z direction).

In order for the optical system to achieve a narrow viewing angle, theoptical path of the light emerging from the second surface 12 issuitably as closely perpendicular to the second surface 12 as possible.In this case, the light emitted from each light source 4 has itsdivergence angle narrowed by an associated light control member 2.However, as shown in FIG. 7A, not all of the light incident through theincident surface 10 travels along an optical path perpendicular to theincident surface 10 within an XY plane but some rays of the light travelalong an optical path spreading in the X direction. Thus, if the prisms3 extend linearly parallel to the X direction as in the embodimentdescribed above, those rays of the light that have been incident on theincident surface 10 impinge obliquely on the reflective surface 30 ofthe prisms 3 within the XY plane. In that case, those light rays totallyreflected from the reflective surface 30 of the prisms 3 do not travelalong an optical path perpendicular to the second surface 12 but travelalong an optical path angled with respect to the second surface 12, thuspossibly decreasing the chances of achieving a narrow viewing angle.

On the other hand, according to this variation, at least part of eachprism 3 is tilted with respect to the incident surface 10 when viewed inthe Z direction. That is to say, according to this variation, the lightincident on the incident surface 10 impinges substantiallyperpendicularly onto the reflective surface 30 of each of the smallprisms 31 within the XY plane. Thus, this variation achieves theadvantage of increasing the chances of the light that has been totallyreflected from the reflective surface 30 of the small prisms 31traveling along an optical path substantially perpendicular to thesecond surface 12, thus eventually achieving a narrow viewing angle moreeasily.

Alternatively, according to this variation, the plurality of smallprisms 31 may also be arranged such that the center of an arc,approximate to the curved pattern, is located opposite from the lightcontrol member 2 with respect to the prism 3 when viewed in the Zdirection as shown in FIG. 7B.

Still alternatively, according to this variation, the plurality of smallprisms 31 may also be arranged not to form a curved pattern when viewedin the Z direction as shown in FIG. 7C. This arrangement achieves theadvantage of requiring a shorter time to perform the patterning processof forming the plurality of small prisms 31. In addition, according tothis arrangement, the plurality of small prisms 31 are arranged atrandom, thus achieving the advantage of more easily reducing theunevenness of the light emerging from the second surface 12.

(3.2) Second Variation

In an optical system 100B according to a second variation, the firstsurface 11 and second surface 12 of the light guide member 1 are nottilted with respect to each other but are both perpendicular to theincident surface 10 as shown in FIGS. 8A and 8B, which is a majordifference from the optical system 100 according to the embodimentdescribed above. In addition, in the optical system 100B according tothis variation, the light sources 4 and the light control members 2 arearranged to be tilted with respect to the incident surface 10, which isanother major difference from the optical system 100 according to theembodiment described above.

That is to say, the optical system 100B according to this variation isdesigned such that most of the light incident on the incident surface 10is directed toward the first surface 11 by making the light sources 4and the light control members 2 tilted with respect to the incidentsurface 10. Thus, according to this variation, most of the lightincident through the incident surface 10 travels, as in the embodimentdescribed above, along the direct optical path L1, thus contributing toincreasing the light extraction efficiency without performing thepatterning process of providing the tilted surface for the light guidemember 1. Consequently, this variation achieves the advantage offacilitating the design of the light guide member 1 compared to theembodiment described above.

Note that although the light guide member 1 includes only the directoptical path L1 in FIG. 8B, the light guide member 1 may also include anindirect optical path L2.

(3.3) Third Variation

In an optical system 100C according to a third variation, the firstsurface 11 and second surface 12 of the light guide member 1 are nottilted with respect to each other but are both perpendicular to theincident surface 10, which is a major difference from the optical system100 according to the embodiment described above. In addition, in theoptical system 100C according to this variation, the plurality of prisms3 (e.g., three prisms 3A, 3B, 3C in this example) have mutuallydifferent depths d1, d2, d3 as shown in FIG. 9, which is another majordifference from the optical system 100 according to the embodimentdescribed above. The respective depths d1, d2, d3 of the three prisms 3increase as the light incident on the incident surface 10 travels deeperinside the light guide member 1 (i.e., to the right in FIG. 9).

That is to say, the optical system 100C according to this variation isdesigned such that most of the light incident through the incidentsurface 10 is totally reflected from any of the plurality of prisms 3 bymaking the respective depths of the plurality of prisms 3 different fromeach other. Thus, according to this variation, most of the lightincident through the incident surface 10 travels, as in the embodimentdescribed above, along the direct optical path L1, thus contributing toincreasing the light extraction efficiency without performing thepatterning process of providing the tilted surface for the light guidemember 1. Consequently, this variation achieves the advantage offacilitating the design of the light guide member 1 compared to theembodiment described above.

Note that although the light guide member 1 includes only the directoptical path L1 in FIG. 9, the light guide member 1 may also include anindirect optical path L2.

(3.4) Other Variations

The embodiment described above may be modified such that the firstsurface 11 is perpendicular to the incident surface 10 and the secondsurface 12 is not perpendicular to the incident surface 10 but is tiltedwith respect to an XY plane. Alternatively, the embodiment describedabove may also be modified such that neither the first surface 11 northe second surface 12 is perpendicular to the incident surface 1010 butboth the first surface 11 and the second surface 12 are tilted withrespect to an XY plane.

Alternatively, the embodiment described above may also be modified suchthat the first surface 11 is provided with only one prism 3, instead ofthe plurality of prisms 3. In that case, the prism 3 may have aplurality of reflective surfaces 30, which are formed over the entirefirst surface 11 and have mutually different tilt angles.

Furthermore, in the embodiment described above, the prisms 3 are formedby patterning an end portion, forming the first surface 11, of the lightguide member 1. However, this is only an example and should not beconstrued as limiting. Alternatively, the prisms 3 may be provided forthe first surface 11 by affixing a prism sheet, on which the prism(s) 3is/are formed, onto the first surface 11. In that case, a single prism 3may be formed on the prism sheet or a plurality of prisms 3 may beformed on the prism sheet.

Furthermore, the prisms 3 may also be divided to be spaced apart fromeach other in the X direction not only in the first variation but alsoin the embodiment, the second variation, and the third variation aswell. Furthermore, the first variation may also be modified such thatthe prism 3 may be a connected one without being divided into theplurality of small prisms 31.

Second Embodiment

(1) Overview

First, an overview of an optical system 1100 according to thisembodiment and an illumination system 1200 including the optical system1100 will be described with reference to FIGS. 10A-12.

An optical system 1100 according to this embodiment (see FIGS. 10A and10B) has the capability of controlling light incident through anincident surface 1010 and allowing the light to emerge from an emergentsurface (second surface 1012). The optical system 1100 includes a lightguide member 1001, a light control member 1002, and a prism 1003 asshown in FIGS. 10A and 10B.

The optical system 1100 forms, along with a light source 1004, anillumination system 1200. In other words, the illumination system 1200according to this embodiment includes the optical system 1100 and thelight source 1004. The light source 1004 emits light to be incident onthe incident surface 1010. As will be described in detail later, if theoptical system 1100 includes a light control member 1002, the lightemitted from the light source 1004 does not enter the light guide member1001 directly but enters the light guide member 1001 indirectly throughthe light control member 1002. That is to say, the light source 1004emits the light toward the incident surface 1010 (of the light guidemember 1001) through the light control member 1002.

As can be seen, according to this embodiment, the optical system 1100includes not only the light guide member 1001 and the prism 1003 butalso the light control member 1002 as well. The light control member1002 is provided between the light source 1004 and the incident surface1010 of the light guide member 1001 to control the light that has beenemitted from the light source 1004 and is going to be incident on theincident surface 1010. Particularly, in this embodiment, the light guidemember 1001 and the light control member 1002 are integrated together asan integrally molded product. That is to say, in this embodiment, thelight guide member 1001 and the light control member 1002 form anintegrally molded product and are inseparable from each other. In otherwords, the light control member 1002 is seamlessly continuous with theincident surface 1010 of the light guide member 1001. That is to say,the light guide member 1001 and the light control member 1002 areintegrated together seamlessly. Thus, in this embodiment, the incidentsurface 1010 of the light guide member 1001 is a “virtual plane” definedinside the integrally molded product of the light guide member 1001 andthe light control member 1002 and is an insubstantial one.

In this embodiment, the light guide member 1001 has the incident surface1010, on which light is incident, and a first surface 1011 and a secondsurface 1012 facing each other. The second surface 1012 is a surfacefrom which the light emerges. The prism 1003 is provided on the firstsurface 1011. The prism 1003 reflects, toward the second surface 1012,the light passing inside the light guide member 1001.

In this embodiment, the light guide member 1001 includes a directoptical path L10 (see FIGS. 10A and 10B). The direct optical path L10 isan optical path, along which the light that has entered the light guidemember 1001 through the incident surface 1010 is directly reflected fromthe prism 3 and allowed to emerge from the second surface 1012. Statedotherwise, the light guide member 1001 includes an optical path (directoptical path L10), along which the light that has entered the lightguide member 1001 through the incident surface 1010 is reflected onlyonce from the prism 1003 inside the light guide member 1001 beforeemerging from the second surface 1012. Once the light has entered thelight guide member 1001 through the incident surface 1010, the lighttraveling along the direct optical path L10 is reflected only once fromthe prism 1003 to reach the second surface 1012 without being reflectedfrom any part other than the prism 1003. Then, the light emerges as itis from the second surface 1012 out of the light guide member 1001.

In this embodiment, most of the light that has entered the light guidemember 1001 through the incident surface 1010 and then emerges from thesecond surface 1012 is guided along the direct optical path L10 insidethe light guide member 1001. Thus, according to this embodiment, most ofthe light that has entered the light guide member 1001 through theincident surface 1010 is reflected only once from the prism 1003,without being reflected from any part other than the prism 1003, beforeemerging from the second surface 1012 out of the light guide member1001.

In the optical system 1100 according to this embodiment, the opticalaxis Ax1 of the light that has been incident through the incidentsurface 1010 is tilted with respect to the first surface 1011 such thatas the distance from the incident surface 1010 increases, the gapdistance between the optical axis Ax1 and the first surface 1011decreases as shown in FIG. 10A. That is to say, in this embodiment, theoptical axis Ax1 of the light incident through the incident surface 1010is not parallel to, but is tilted with respect to, the first surface1011, and comes closer toward the first surface 1011 due to its tilt, asthe distance from the incident surface 1010 increases.

Thus, the light that has been incident through the incident surface 1010comes closer toward the first surface 1011 as the light goes fartheraway from the incident surface 1010 (i.e., as the light goes deeperinside the light guide member 1001). This allows the light to beincident on the first surface 1011 (including the prisms 1003) moreeasily. This facilitates most of the light that has been incidentthrough the incident surface 1010 being incident on the first surface1011 before reaching the end surface 1013, facing the incident surface1010, of the light guide member 1001. In other words, this reduces thechances of most of the light that has been incident through the incidentsurface 1010 reaching the end surface 1013, located opposite from theincident surface 1010, of the light guide member 1001, thus reducingleakage of light from the end surface 1013. Consequently, this mayincrease the proportion of the light emerging from the second surface1012 out of the light guide member 1001 after having traveled along thedirect optical path L10 to the overall light that has been incidentthrough the incident surface 1010, thus contributing to increasing thelight extraction efficiency.

In addition, in the optical system 1100 according to this embodiment,the light control member 1002 has a shape transformation function asshown in FIG. 11. As used herein, the shape transformation function isthe function of transforming the shape of the light projected onto aprojection plane S1 parallel to the incident surface 1010 from a firstshape F1 of the light emitted from the light source 1004 into a secondshape F2 of the light that is going to be incident on the incidentsurface 1010. In this case, the projection plane S1 is a “virtual plane”defined inside the light control member 1002 and is an insubstantialone. In this embodiment, the projection plane S1 is supposed to be thesame plane as the incident surface 1010, for example. That is to say, inthis embodiment, the light control member 1002 provided between thelight source 1004 and the incident surface 1010 of the light guidemember 1001 transforms the shape of the light projected onto theprojection plane S1 parallel to the incident surface 1010 (i.e., theincident surface 1010 in this embodiment) from the first shape F1 intothe second shape F2.

This makes the range that the light incident through the incidentsurface 1010 may reach inside the light guide member 1001 controllableirrespective of the first shape F1 that is the shape of the lightemitted from the light source 1004. That is to say, the range that thelight incident through the incident surface 1010 may reach inside thelight guide member 1001 derives from the second shape F2 that is theshape of the light incident on the incident surface 1010. This opticalsystem 1100 may transform the shape from the first shape F1 into thesecond shape F2. Thus, this optical system 1100 may control the lightincident through the incident surface 1010 so that the light may reach arelatively broad range inside the light guide member 1001. Consequently,this optical system 1100 increases the chances of the light reaching theentire first surface 1011, thus facilitating uniformly extracting thelight from the entire second surface 1012 serving as an emergentsurface.

In addition, in the optical system 1100 according to this embodiment, atleast one of the first surface 1011 or the second surface 1012 includesa luminous intensity distribution control member 1014 as shown in FIG.12. The luminous intensity distribution control member 1014 controls theluminous intensity distribution of the light extracted from the secondsurface 1012. In this embodiment, only the second surface 1012, out ofthe first surface 1011 and the second surface 1012, includes theluminous intensity distribution control member 1014 as an example. Thatis to say, the luminous intensity distribution control member 1014 isprovided for the second surface 1012.

This enables the luminous intensity distribution of the light extractedfrom the second surface 1012 of the light guide member 1001 to becontrolled by the luminous intensity distribution control member 1014provided for the light guide member 1001. In particular, the light guidemember 1001 includes a direct optical path L10, along which the lightthat has entered the light guide member 1001 through the incidentsurface 1010 is reflected only once from the prism 1003 inside the lightguide member 1001 before emerging from the second surface 1012. That isto say, the light traveling along the direct optical path L10 isreflected, after having entered the light guide member 1001 through theincident surface 1010, only once from the prism 1003, without beingreflected from any part other than the prism 1003, before emerging fromthe second surface 1012 out of the light guide member 1001. Thus, theshapes of the first surface 1011 and the second surface 1012 do notcontribute to guiding the light inside the light guide member 1001.Therefore, even if the luminous intensity distribution control member1014 is provided for the light guide member 1001, the light guidingperformance of the light guide member 1001 hardly deteriorates.Consequently, this allows the light traveling along the direct opticalpath L10 to be extracted efficiently from the second surface 1012 out ofthe light guide member 1001 while enabling the luminous intensitydistribution to be controlled, thus contributing to increasing the lightextraction efficiency.

Furthermore, as shown in FIG. 11, an optical member 1020 for use as thelight control member 1002 in the optical system 1100 according to thisembodiment includes an incident lens 1021 and an outlet portion 1022.The optical member 1020 allows the light that has been incident on theincident lens 1021 from the light source 1004 to go out of the opticalmember 1020 from the outlet portion 1022. The incident lens 1021 has amain incident surface 1211 and an auxiliary incident surface 1212. Themain incident surface 1211 is arranged to face the light source 1004.The auxiliary incident surface 1212 is arranged to face toward a normalL21 to the main incident surface 1211. The auxiliary incident surface1212 is located at least partially along a circumference of the mainincident surface 1211. An optical axis Ax2 of the light source 1004 istilted with respect to the normal L21 to the main incident surface 1211.In this case, if the main incident surface 1211 has a dome shape, thenormal L21 to the main incident surface 1211 is a normal to the mainincident surface 1211 at a tip portion (i.e., a peak portion of thedome) thereof. The normal L21 to the main incident surface 1211 is a“virtual line” and is an insubstantial one.

Since the optical axis Ax2 of the light source 1004 is tilted withrespect to the normal L21 to the main incident surface 1211, the lightemitted from the light source 1004 is incident on the incident lens 1021of the optical member 1020 asymmetrically to the normal L21 to the mainincident surface 1211. This allows making the intensity of the lightincident from the light source 1004 imbalanced between the main incidentsurface 1211 of the incident lens 1021 and the auxiliary incidentsurface 1212 located around the main incident surface 1211.Consequently, this allows the optical member 1020 to have increasedlight harvesting efficiency.

(2) Details

Next, the optical system 1100 according to this embodiment, anillumination system 1200 including the optical system 1100, a displaysystem 300 including the illumination system 1200, and a moving vehicleB1 will be described in detail with reference to FIGS. 10A-21C.

(2.1) Premise

In the following description, a width direction defined with respect tothe light guide member 1001 (i.e., a direction in which the plurality oflight sources 1004 are arranged side by side in FIG. 12) will behereinafter referred to as an “X-axis direction” and a depth directiondefined with respect to the light guide member 1001 (i.e., a directionin which the optical axis Ax1 extends in FIG. 10A) will be hereinafterreferred to as a “Y-axis direction.” Furthermore, in the followingdescription, a thickness direction defined with respect to the lightguide member 1001 (i.e., a direction in which the first surface 1011 andthe second surface 1012 are arranged one on top of the other in FIG.10A) will be hereinafter referred to as a “Z-axis direction.” The X-,Y-, and Z-axes defining these directions are perpendicular to eachother. Note that the arrows indicating the “X-axis direction,” “Y-axisdirection,” and “Z-axis direction” on the drawings are shown there justas an assistant to description and are insubstantial ones.

As used herein, the “extraction efficiency” refers to the proportion ofthe quantity of the light emerging from the second surface 1012(emergent surface) of the light guide member 1001 with respect to thequantity of the light incident on the incident surface 1010 of the lightguide member 1001. That is to say, as the proportion of the quantity ofthe light emerging from the second surface 1012 of the light guidemember 1001 with respect to the quantity of the light incident on theincident surface 1010 of the light guide member 1001 increases, thelight extraction efficiency increases (rises). For example, supposingthe quantity of the light emerging from the second surface 1012 is “10”while the quantity of the light incident on the incident surface 1010 ofthe light guide member 1001 is “100,” then the light extractionefficiency of the light guide member 1001 is 10%.

Also, as used herein, the “harvesting efficiency” refers to theproportion of the quantity of light entering the optical member 1020(light control member 1002) with respect to the quantity of lightemitted (or output) from the light source 1004. That is to say, as theproportion of the quantity of the light entering the optical member 1020with respect to the quantity of the light output from the light source1004 increases, the light harvesting efficiency increases (rises). Forexample, supposing the quantity of the light entering the optical member1020 is “10” while the quantity of the light output from the lightsource 1004 is “100,” the light harvesting efficiency of the opticalmember 1020 is 10%.

Furthermore, as used herein, the “optical axis” refers to a virtuallight ray representing a light beam passing through the entire system.For example, the optical axis Ax2 of the light source 1004 agrees withthe axis of rotational symmetry of the light emitted from the lightsource 1004.

Furthermore, as used herein, if something is “parallel to” somethingelse, this expression means that these two things are substantiallyparallel to each other. That is to say, these two things may naturallybe exactly parallel to each other but may also form an angle withinseveral degrees (e.g., less than 5 degrees) between themselves.

Likewise, as used herein, if something is “perpendicular to” somethingelse, this expression means that these two things are substantiallyperpendicular to each other. That is to say, these two things maynaturally be exactly perpendicular to each other but may also form anangle within 90±several degrees (e.g., 90±less than 5 degrees) betweenthemselves.

(2.2) Display System

First, the display system 1300 will be described with reference to FIGS.13 and 14.

The illumination system 1200 according to this embodiment forms, alongwith a display 1005, a display system 1300 as shown in FIG. 13. In otherwords, the display system 1300 according to this embodiment includes theillumination system 1200 and the display 1005. The display 1005 receivesthe light emerging from the illumination system 1200 and displays animage thereon. As used herein, the “image” refers to an image displayedin such a mode that allows the user U1 (see FIG. 14) to view the imageand may be a figure, a sign, a character, a numeral, a pattern, a photo,or a combination thereof. Examples of the images displayed by thedisplay system 300 include a moving picture (movie) and a still picture(still image). Furthermore, the “moving picture” further includes animage composed of a plurality of still pictures captured by stop motionshooting, for example.

In addition, the display system 1300 according to this embodiment forms,along with the moving vehicle body B11, a moving vehicle B1 such as anautomobile as shown in FIG. 14. In other words, the moving vehicle B1according to this embodiment includes the display system 1300 and themoving vehicle body B11. The moving vehicle body B11 is equipped withthe display system 1300. In this embodiment, the moving vehicle B1 issupposed to be an automobile to be driven by a human (i.e., a passengercar), as an example. In that case, the user U1 who views the imagedisplayed by the display system 1300 is a passenger on the movingvehicle B1. In this embodiment, the user U1 is supposed to be the driverof the automobile as the moving vehicle B1 as an example.

In this embodiment, the display system 1300 may be used in, for example,a head-up display (HUD) to be installed in the moving vehicle B1. Thedisplay system 1300 is used to present, within the user's U1 sight,various types of driver assistance information including velocityinformation, condition information, and driving-related informationabout the moving vehicle B1. Examples of the driving-related informationabout the moving vehicle B1 include navigation-related informationpresenting proposed traveling routes, for example, and adaptive cruisecontrol (ACC) related information for use to keep the traveling velocityand the distance between the vehicles constant.

As shown in FIGS. 13 and 14, the display system 1300 includes an imagedisplay unit 1310, an optical system 1320, and a control unit 1330. Thedisplay system 1300 further includes a housing 1340 for housing theimage display unit 1310, the optical system 1320, and the control unit1330 therein.

The housing 1340 may be a molded product of a synthetic resin, forexample. In the housing 1340, housed are the image display unit 1310,the optical system 1320, the control unit 1330, and other members. Thehousing 1340 is installed in a dashboard B13 of the moving vehicle bodyB11. The light reflected from a second mirror 1322 (to be describedlater) of the optical system 1320 passes through an opening providedthrough the upper surface of the housing 1340 to emerge toward areflective member (windshield B12). Then, the light is reflected fromthe windshield B12 and condensed into an eye box C1. The reflectivemember does not have to be the windshield B12 but may also beimplemented as, for example, a combiner provided on the dashboard B13 ofthe moving vehicle body B11.

This display system 1300 allows the user U1 to view, through thewindshield B12, a virtual image projected toward the space in front ofthe moving vehicle B1 (outside of the automobile B1). As used herein,the “virtual image” refers to an image formed by a ray of the lightemerging from the display system 1300 and diverging from the windshieldB12 or any other reflective member as if there actually were an objectin the space. This allows the user U1 who is driving the moving vehicleB1 to view the image as a virtual image projected by the display system1300 and superimposed on the real space in front of the moving vehicleB1. In short, the display system 1300 according to this embodimentdisplays a virtual image as an image. Examples of the images (virtualimages) to be displayed by the display system 1300 include a virtualimage E1 superimposed along the traveling surface D1 of the movingvehicle B1 and a virtual image to be rendered stereoscopically along aplane PL1 perpendicular to the traveling surface D1.

The image display unit 1310 includes a case 1311. The image display unit1310 has the capability of displaying a stereoscopic image by the lightfield method, according to which an object in an image captured is madeto look stereoscopic by reproducing light beams emerging from the objectin a plurality of directions. Note that the light field method is notthe only method allowing the image display unit 1310 to display thevirtual image of the stereoscopic rendering target stereoscopically.Alternatively, the image display unit 1310 may also adopt a parallaxmethod, which allows the user U1 to view a virtual image of thestereoscopic rendering target by projecting a pair of images with aparallax onto the user's U1 right and left eyes, respectively.

The image display unit 1310 includes the display 1005 and theillumination system 1200 including the optical system 1100. The display1005 may be implemented as, for example, a liquid crystal display, andreceives the light emerging from the illumination system 1200 to displayan image thereon. That is to say, the illumination system 1200 emitslight from behind the display 1005 toward the display 1005. The lightthat has come from the illumination system 1200 is transmitted throughthe display 1005, thus allowing the display 1005 to display an imagethereon. In other words, the illumination system 1200 serves as abacklight for the display 1005.

The image display unit 1310 includes a case 1311. In the case 1311,housed are the illumination system 1200 including the optical system1100 and the light source 1004 and the display 1005. The illuminationsystem 1200 and the display 1005 are held by the case 1311. In thisembodiment, the display 1005 is arranged along the upper surface of thecase 1311 and one surface of the display 1005 is exposed on the uppersurface of the case 1311. The illumination system 1200 is arranged underthe display 1005 inside the case 1311 to emit light toward the display1005 from under the display 1005. Thus, the upper surface of the case1311 constitutes a display screen 1312 on which the image is displayed.

The image display unit 1310 is housed in the internal space of thehousing 1340 such that the display screen 1312 thereof faces a firstmirror 1321 (to be described later). The display screen 1312 of theimage display unit 1310 has a shape (e.g., a rectangular shape)corresponding to the range of the image to be projected toward the userU1 (i.e., the shape of the windshield B12). On the display screen 1312of the image display unit 1310, a plurality of pixels are arranged toform an array. The plurality of pixels of the image display unit 1310emits light beams under the control of the control unit 1330. As aresult, an image to be displayed on the display screen 1312 is formed bythe light beams emerging from the display screen 1312 of the imagedisplay unit 1310.

The light representing the image displayed on the display screen 1312 ofthe image display unit 1310 emerges from the display screen 1312 towardthe windshield B12. Then, the light is reflected from the windshield B12and condensed into the eye box C1. That is to say, the image displayedon the display screen 1312 is viewed, through the optical system 1320,by the user U1 who has a viewpoint inside the eye box C1. At this time,the user U1 views, through the windshield B12, the virtual imageprojected onto a space in front of the moving vehicle B1 (i.e., outsideof the moving vehicle B1).

The optical system 1320 condenses the light emerging from the displayscreen 1312 of the image display unit 1310 into the eye box C1. In thisembodiment, the optical system 1320 includes: the first mirror 1321,which may be a convex mirror, for example; the second mirror 1322, whichmay be a concave mirror; and the windshield B12.

The first mirror 1321 reflects the light emerging from the image displayunit 1310 to make the light incident on the second mirror 1322. Thesecond mirror 1322 reflects the light, which has been incident thereonfrom the first mirror 1321, toward the windshield B12. The windshieldB12 reflects the light, which has been incident thereon from the secondmirror 1322, to make the light incident into the eye box C1.

The control unit 1330 includes a computer system, for example. Thecomputer system may include one or more processors and one or morememories as principal hardware components. The functions of the controlunit 1330 (e.g., the functions of a rendering control unit 1331, animage data producing unit 1332, and an output unit 1333) may beperformed by making the one or more processors execute a program storedin the one or more memories or a storage unit 1334 of the computersystem. The program may be stored in advance in the one or more memoriesor the storage unit 1334 of the computer system. Alternatively, theprogram may also be downloaded through a telecommunications line or bedistributed after having been recorded in some non-transitory storagemedium such as a memory card, an optical disc, or a hard disk drive, anyof which is readable for the computer system.

The storage unit 1334 may be implemented as, for example, anon-transitory storage medium such as a programmable nonvolatilesemiconductor memory. The storage unit 1334 stores a program to beexecuted by the control unit 1330 and other data. In addition, thedisplay system 1300 is used to present, within the user's U1 sight,driver assistance information including velocity information, conditioninformation, and driving information about the moving vehicle B1. Thus,the types of the virtual images displayed by the display system 1300 aredetermined in advance. The image data to display the virtual images(including a virtual image E1 as a plane rendering target and a virtualimage as a stereoscopic rendering target) is stored in advance in thestorage unit 1334.

The rendering control unit 1331 receives detection signals from varioussensors 1350 installed in the automobile B1. The sensors 1350 may besensors for detecting various types of information for use in anadvanced driver assistance system (ADAS), for example. The sensors 1350include at least one sensor selected from the group consisting ofsensors for detecting the conditions of the moving vehicle B1 andsensors for detecting the circumstances surrounding the moving vehicleB1. Examples of such sensors for detecting the conditions of the movingvehicle B1 include sensors for measuring the velocity, temperature, andresidual fuel of the moving vehicle B1. Examples of such sensors fordetecting the circumstances surrounding the moving vehicle B1 include animage sensor, a milli-wave radar, or a light detection and ranging(LiDAR) sensor for shooting video presenting the surroundings of themoving vehicle B1.

The rendering control unit 1331 acquires, in accordance with thedetection signals supplied from the sensors 1350, a single or multipleitems of image data for displaying information about the detectionsignals from the storage unit 1334. In this case, when multiple types ofinformation are displayed on the image display unit 1310, the renderingcontrol unit 1331 acquires multiple items of image data for displayingthe multiple types of information. In addition, the rendering controlunit 1331 also obtains, in accordance with the detection signalssupplied from the sensors 1350, location information about the displaylocation of the virtual image in a target space where the virtual imageis displayed. Then, the rendering control unit 1331 outputs the imagedata of the virtual image(s) to display and the location informationthereof to the image data producing unit 1332.

The image data producing unit 1332 produces, based on the image data andlocation information provided by the rendering control unit 1331, imagedata for displaying the virtual image(s) to display.

The output unit 1333 outputs the image data that has been produced bythe image data producing unit 1332 to the image display unit 1310 tohave an image based on the produced image data displayed on the displayscreen 1312 of the image display unit 1310. Light representing the imagedisplayed on the display screen 1312 is projected onto the windshieldB12, thus having the image (virtual image) displayed by the displaysystem 1300. In this manner, the image (virtual image) displayed by thedisplay system 300 is viewed by the user U1.

(2.3) Optical System

Next, the optical system 1100 will be described with reference to FIGS.10A-12 and FIGS. 15A-16B.

In this embodiment, the optical system 1100 includes a light guidemember 1001, a plurality of light control members 1002, and a pluralityof prisms 1003. That is to say, the optical system 1100 according tothis embodiment includes a plurality of light control members 1002 and aplurality of prisms 1003.

Also, in this embodiment, the optical system 1100 forms, along with theplurality of light sources 1004, the illumination system 1200. In otherwords, the illumination system 1200 according to this embodimentincludes the optical system 1100 and the plurality of light sources1004.

A common configuration is adopted for the plurality of light controlmembers 1002. Thus, unless otherwise stated, the description of aconfiguration for a single light control member 1002 is equallyapplicable to the other light control members 1002 as well. Likewise, acommon configuration is adopted for the plurality of prisms 1003. Thus,unless otherwise stated, the description of a configuration for a singleprism 1003 is equally applicable to the other prisms 1003 as well.Likewise, a common configuration is adopted for the plurality of lightsources 1004. Thus, unless otherwise stated, the description of aconfiguration for a single light source 1004 is equally applicable tothe other light sources 1004 as well.

The light sources 1004 are each implemented as a solid-statelight-emitting element such as a light-emitting diode (LED) or anorganic electroluminescent (OEL) element. In this embodiment, each lightsource 1004 is implemented as a light-emitting diode element with a chipshape. Such a light source 1004 actually emits light from a certain areaof its surface (light-emitting surface). Ideally, such a light source1004 may be regarded as a point light source which emits light from apoint on its surface. Thus, in the following description, the lightsource 1004 will be described on the supposition that the light source1004 is an ideal point light source.

In this embodiment, the light source 1004 is arranged to face theincident surface 1010 of the light guide member 1001 with apredetermined interval left between the light source 1004 and theincident surface 1010 as shown in FIG. 11. In addition, the lightcontrol member 1002 is provided between the light source 1004 and theincident surface 1010 of the light guide member 1001.

In this embodiment, the light control member 1002 is integrated with thelight guide member 1001. As used herein, if a plurality of elements (orportions) are “integrated” with each other, this phrase refers to anarrangement in which the plurality of elements may be handled as aphysically integrated one. That is to say, the expression “a pluralityof elements are integrated together” herein refers to an arrangement inwhich the plurality of elements are aggregated together and may behandled as if those elements were a single member. In that case, thoseelements may be integrated together and inseparable from each other asin an integrally molded product. Alternatively, a plurality of elementsthat have been formed separately may be mechanically joined together bywelding, bonding, or caulking, for example. That is to say, the lightguide member 1001 and the light control member 1002 may be integratedtogether in any appropriate manner.

More specifically, in this embodiment, the light guide member 1001 andthe light control member 1002 are integrated together to form anintegrally molded product as described above. That is to say, in thisembodiment, the light guide member 1001 and the light control member1002 form an integrally molded product and are integrated andinseparable from each other. Thus, the incident surface 1010 of thelight guide member 1001 is a “virtual plane” defined inside theintegrally molded product of the light guide member 1001 and the lightcontrol member 1002 as described above and is an insubstantial one.

In this embodiment, the plurality of light sources 1004 are arranged atregular intervals in the X-axis direction as shown in FIG. 12. Each ofthe plurality of light sources 4 is provided one to one for anassociated one of the plurality of light control members 2. That is tosay, the plurality of light control members 1002, as well as theplurality of light sources 1004, are also arranged side by side in theX-axis direction. In this case, the arrangement pitch of the pluralityof light sources 1004 in the X-axis direction is equal to thearrangement pitch of the plurality of light control members 1002 in theX-axis direction.

The light guide member 1001 allows the light emitted from the lightsources 1004 to enter the light guide member 1001 itself through theincident surface 1010 and guides the light thus entered toward thesecond surface 1012 as an emergent surface by letting the light passinside the light guide member 1001 itself. That is to say, the lightguide member 1001 is member for guiding the light. In this embodiment,the light guide member 1001 is a molded product of a light-transmittingresin material such as an acrylic resin and is formed in the shape of aplate. That is to say, the light guide member 1001 is a light guideplate having a certain thickness.

The light guide member 1001 has the incident surface 1010 on which thelight is incident, and a first surface 1011 and a second surface 1012(emergent surface) that face each other. The light guide member 1001further has an end surface 1013 facing the incident surface 1010.

Specifically, in this embodiment, the light guide member 1001 has arectangular plate shape and the two surfaces thereof facing each otherin the thickness direction defined with respect to the light guidemember 1001 are the first surface 1011 and the second surface 1012,respectively, as shown in FIGS. 15A-15D. Also, one of the four endsurfaces (peripheral surfaces) of the light guide member 1001 is theincident surface 1010. That is to say, the light guide member 1001 isformed in a rectangular shape in a plan view (i.e., when viewed from oneend in the Z-axis direction). In this embodiment, the light guide member1001 may be formed, for example, in the shape of a rectangle, of whichthe dimension measured in the Y-axis direction is smaller than itsdimension measured in the X-axis direction. In addition, both surfacesin the thickness direction (i.e., the Z-axis direction) defined withrespect to the light guide member 1001 constitute the first surface 1011and the second surface 1012, respectively. Furthermore, both surfaces inthe latitudinal direction (i.e., the Y-axis direction) defined withrespect to the light guide member 1001 constitute the incident surface1010 and the end surface 1013, respectively.

As can be seen, one end surface (i.e., the left surface in FIG. 10A) outof the two end surfaces, facing each other in the Y-axis direction, ofthe light guide member 1001 is the incident surface 1010, on which thelight beams emitted from the plurality of light sources 1004 areincident through the plurality of light control members 1002. The twosurfaces, facing each other in the Z-axis direction, of the light guidemember 1001 are the first surface 1011 and the second surface 1012,respectively. The first surface 1011 corresponds to the lower surface inFIG. 10A and the second surface 1012 corresponds to the upper surface inFIG. 10A. In addition, the second surface 1012 is an emergent surface,through which the light emerges from inside to outside of the lightguide member 1001. Thus, letting the light enter the light guide member1001 through one end surface serving as the incident surface 1010 allowsthe second surface 1012, serving as an emergent surface, to providesurface-emitting light.

Furthermore, in this embodiment, the second surface 1012 is a planeparallel to an X-Y plane and the incident surface 1010 is a planeparallel to an X-Z plane. As used herein, the “X-Y plane” refers to aplane that includes the X-axis and the Y-axis and that intersects atright angles with the Z-axis. Likewise, as used herein, the “X-Z plane”refers to a plane that includes the X-axis and the Z-axis and thatintersects at right angles with the Y-axis. In other words, the secondsurface 1012 is a plane that intersects at right angles with the Z-axisand the incident surface 1010 is a plane that intersects at right angleswith the Y-axis. Thus, the second surface 1012 and the incident surface1010 intersect at right angles with each other.

On the other hand, the first surface 1011 is a plane that is notparallel to, but tilted with respect to, the X-Y plane. That is to say,the first surface 1011 and the incident surface 1010 do not intersect atright angles with each other. Specifically, the first surface 1011 istilted with respect to the X-Y plane such that as the distance from theincident surface 1010 increases, the first surface 1011 comes closertoward the second surface 1012. That is to say, in this embodiment, thefirst surface 1011 and the second surface 1012 are tilted with respectto each other.

Furthermore, according to this embodiment, the second surface 1012 isprovided with the luminous intensity distribution control member 1014.The luminous intensity distribution control member 1014 includes a lens.In this embodiment, the luminous intensity distribution control member1014 includes a cylindrical lens as an example. The luminous intensitydistribution control member 1014 will be described in detail later inthe “(2.7) Luminous intensity distribution control member” section.

The light control members 1002 are arranged between the light sources1004 and the incident surface 1010 of the light guide member 1001. Eachof the light control members 1002 controls the light that has beenemitted from an associated one of the light sources 1004 and is going tobe incident on the incident surface 1010. In this embodiment, each lightcontrol member 1002 has the capability of substantially collimating thelight emitted from the associated light source 1004 into parallel rays.That is to say, the light control member 1002 is a collimator lens whichcondenses, toward the incident surface 1010, the radially divergentlight that has come from the light source 1004, thereby substantiallycollimating the incident light into parallel rays. In this case, thelight emitted from the light source 1004 is incident on the incidentsurface 1010 of the light guide member 1001 through the light controlmember 1002. Thus, the light emitted from the light source 1004 iscontrolled to have its divergence angle narrowed by the light controlmember 1002 with the collimating capability and directed toward theincident surface 1010 of the light guide member 1001. In the followingdescription, this embodiment will be described on the supposition thatthe light emitted from the light source 1004 serving as an ideal pointlight source is controlled by the light control member 1002 to becollimated into ideal parallel rays.

As will be described in detail later in the “(2.4) Obliquely incidentlight” section, the optical axis Ax1 of the light incident through theincident surface 1010 of the light guide member 1001 is tilted in thisembodiment with respect to the first surface 1011 such that as thedistance from the incident surface 1010 increases, the gap distancebetween the optical axis Ax1 and the first surface 1011 decreases asshown in FIG. 10A. Thus, the parallel rays directed from the lightcontrol member 1002 toward the incident surface 1010 of the light guidemember 1001 are parallel rays tilted with respect to the first surface1011 such that as the distance from the incident surface 1010 increases,the gap distance between the parallel rays and the first surface 1011decreases. Note that the dotted arrows shown on the drawings indicatethe light rays (or optical paths) just conceptually and areinsubstantial ones.

In this embodiment, the plurality of light control members 1002 areprovided for the end portion, serving as the incident surface 1010, ofthe light guide member 1001 to be arranged side by side in the X-axisdirection as shown in FIG. 12. That is to say, in this embodiment, thelight control members 1002 are integrated with the light guide member1001. In addition, the plurality of light control members 1002correspond one to one to the plurality of light sources 1004 asdescribed above. Thus, each of the plurality of light control members1002 controls the divergence angle of the light emitted from anassociated one of the light sources 1004 and directs the light towardthe incident surface 1010. The shape of the light control member 1002will be described in detail later in the “(2.5) Shape transformationfunction” section and the “(2.6) Asymmetric shape” section.

The prisms 1003 are provided for the first surface 1011 and is eachconfigured to reflect the light passing inside the light guide member1001 toward the second surface 1012. In this embodiment, a plurality ofprisms 1003 are provided for the first surface 1011. Each of the prisms1003 is configured to totally reflect the incident light. Naturally, theprism 1003 does not have to be configured to totally reflect all theincident light. Alternatively, according to another arrangement, part ofthe incident light is not totally reflected but may pass through theinside of the prism 1003.

In the light guide member 1001, most of the light that has entered thelight guide member 1001 through the incident surface 1010 is reflectedfrom the prisms 1003, without being reflected from the rest of the firstsurface 1011 or the second surface 1012 other than the prisms 3, beforeemerging from the second surface 1012. That is to say, the light guidemember 1001 includes a direct optical path L10, along which the lightthat has entered the light guide member 1001 through the incidentsurface 1010 is directly reflected from the prisms 1003 and allowed toemerge from the second surface 1012.

In this embodiment, the prisms 3 are each formed on the first surface1011 such that its cross section as viewed from one end in the X-axisdirection forms a triangular recess. The prisms 1003 may be formed bypatterning the first surface 1011 of the light guide member, forexample. Each prism 1003 has a reflective surface 1030 for reflecting,toward the second surface 1012, the light that has been incident thereonby passing inside the light guide member 1001 as shown in FIG. 10B. Notethat FIG. 10B is a schematic representation providing an enlarged viewof the end surface region A1 encircled with a one-dot chain circle inFIG. 10A.

The angle θ1 formed between the reflective surface 1030 and the firstsurface 1011 (i.e., the tilt angle of the reflective surface 1030) isdefined such that the angle of incidence θ0 of the light incident on thereflective surface 1030 becomes equal to or greater than a criticalangle. That is to say, the reflective surface 1030 is tilted withrespect to the first surface 1011 to totally reflect the incident light.In addition, the tilt angle θ1 of the reflective surface 1030 is alsoset such that the light totally reflected from the reflective surface1030 is incident perpendicularly onto the second surface 1012.

In this embodiment, the plurality of prisms 1003 are arranged in azigzag pattern on the first surface 1011 as shown in FIGS. 16A and 16Bwhen viewed from one end in the Z-axis direction. FIG. 16A is aschematic plan view illustrating, on a larger scale, the region A1 shownin FIG. 15C. FIG. 16B schematically illustrates a cross section of anend surface taken along the plane B1-B1 shown in FIG. 16A. Although onlya part of the first surface 1011 is shown in FIG. 16A, a plurality ofprisms 1003 are actually formed over almost the entire area of the firstsurface 1011.

Specifically, each prism 1003 has a length in the X-axis direction. Theplurality of prisms 1003 are arranged to be spaced from each other alongthe longitudinal axis thereof (i.e., in the X-axis direction). Inaddition, the plurality of prisms 1003 are also arranged to be spacedapart from each other in the Y-axis direction. Supposing multiple banksof prisms 1003, each being arranged in the X-axis direction, are counteda first bank, a second bank, a third bank, and so on, from the onelocated closest to the incident surface 1010 in the Y-axis direction,the plurality of prisms 1003 included in an even-numbered bank areshifted in the X-axis direction from the plurality of prisms 1003included in an odd-numbered bank. In this embodiment, the plurality ofprisms 1003 included in the even-numbered bank and the plurality ofprisms 1003 included in the odd-numbered bank are arranged such thattheir longitudinal ends (in the X-axis direction) overlap with eachother in the Y-axis direction. According to such an arrangement, theplurality of prisms 1003 are densely arranged in the X-axis directionwith no gap left between themselves when viewed from the incidentsurface 1010. This allows the light that has entered the light guidemember 1001 through the incident surface 1010 to be reflected from anyof the plurality of prisms 1003.

In this embodiment, the plurality of prisms 1003 may all have the sameshape, for example. Therefore, in the plurality of prisms 1003 arrangedin the Y-axis direction, their respective reflective surfaces 1030 havethe same tilt angle θ1 as shown in FIG. 16B. In addition, the dimensionsof prisms 1003, including the respective longitudinal dimensions of theprisms 1003 and the respective depths of the recesses serving as theprisms 1003 (in other words, the respective heights of the prisms 1003)are the same between the plurality of prisms 1003. That is to say, inthis embodiment, a plurality of prisms 1003 are arranged side by side inthe direction in which the light is incident on the incident surface1010 (i.e., in the Y-axis direction). In this case, the plurality ofprisms 1003 have the same shape. Thus, if the angle of incidence θ0 ofthe light incident on the reflective surfaces 1030 is constant, then thelight is reflected in the same direction from the respective reflectivesurfaces 1030 of the prisms 1003, no matter which of the plurality ofprisms 1003 the light has been incident on. This allows all the lightbeams reflected from the plurality of prisms 1003 to be incidentperpendicularly onto the second surface 1012.

Furthermore, the recesses serving as the prisms 1003 may have a depth(in other words, the prisms 1003 may have a height) falling within therange from 1 μm to 100 μm, for example. Likewise, the plurality ofprisms 1003 may have an arrangement pitch in the Y-axis directionfalling within the range from 1 μm to 1000 μm, for example. As aspecific example, the recesses serving as the prisms 1003 may have adepth of 10-odd μm and the plurality of prisms 1003 may have anarrangement pitch in the Y-axis direction of 100 and a few ten μm.

Next, the light emission principle of the optical system 1100 accordingto this embodiment will be described with reference to FIGS. 10A and10B.

First, as shown in FIG. 10A, the light emitted from each light source1004 has its divergence angle controlled by passing through anassociated light control member 1002. Then, the light with thedivergence angle thus controlled travels from the light control member1002 toward the incident surface 1010 of the light guide member 1001. Inthis embodiment, the light transmitted through the light control member1002 turns into parallel rays, which are parallel to the second surface1012 and are incident perpendicularly onto the incident surface 1010.

Also, as described above, the optical axis Ax1 of the light that hasentered the light guide member 1001 through the incident surface 1010 istilted with respect to the first surface 1011 such that as the distancefrom the incident surface 1010 increases, the gap distance between theoptical axis Ax1 and the first surface 1011 decreases. Thus, most of thelight incident through the incident surface 1010 reaches the firstsurface 1011 without reaching the second surface 1012 or the end surface1013, facing the incident surface 1010, of the light guide member 1001.

Then, as shown in FIG. 10B, most of the light incident through theincident surface 10 is totally reflected from the reflective surface1030 of any of the plurality of prisms 1003 provided for the firstsurface 1011, without being reflected from the first surface 11 or thesecond surface 12. That is to say, the light guide member 1 includes adirect optical path L10, along which the light that has entered thelight guide member 1 through the incident surface 1010 is directlyreflected from the prisms 3 and allowed to emerge from the secondsurface 1012. Furthermore, in this embodiment, the direct optical pathL10 includes the optical paths of the light beams totally reflected fromthe prisms 1003. The light beams totally reflected from the respectivereflective surfaces 1030 of the prisms 1003 travel along the opticalpaths that intersect at right angles with the second surface 1012 beforeemerging from the second surface 1012.

In this embodiment, the respective reflective surfaces 1030 of theplurality of prisms 1003 all have the same tilt angle θ1 as describedabove. When parallel beams, which are parallel to the second surface1012, are incident on the plurality of prisms 1003, the angles ofincidence θ0 defined by the light beams incident on the reflectivesurfaces 1030 also become constant. Thus, the light is reflected in thesame direction from the reflective surface 1030 of any of the pluralityof prisms 1003. Consequently, in this embodiment, every light beamreaching the second surface 1012 after having traveled along the directoptical path L10 is incident on the second surface 1012 at the sameangle. As used herein, the “same angle” does not have to be exactly thesame angle but may also refer to two angles which are slightly differentfrom each other by not more than 2 or 3 degrees. Ideally, every lightbeam reaching the second surface 1012 after having traveled along thedirect optical path L10 is incident on the second surface 1012 to forman angle of 90 degrees with respect to (i.e., perpendicularly to) thesecond surface 1012.

In this embodiment, the plurality of prisms 1003 are arranged over theentire area of the second surface 1012, and therefore, the light thathas traveled along the direct optical path L10 described above emergesuniformly from the entire second surface 1012 of the light guide member1001. This allows the entire second surface 1012 to providesurface-emitting light.

Next, an advantage to be achieved by the optical system 1100 accordingto this embodiment will be described in comparison with a general lightguide member (light guide plate).

In the general light guide member, the light that has entered the lightguide member through an incident surface thereof is guided inside thelight guide member while being reflected a number of times from bothsurfaces along the thickness (corresponding to the first surface 1011and the second surface 1012) of the light guide member. Then, thecondition for the total reflection (i.e., angle of incidence≥criticalangle) is no longer satisfied when the light is reflected from a prismprovided for one surface (corresponding to the first surface 1011) alongthe thickness of the light guide member. As a result, the light emergesfrom the other surface, serving as an emergent surface (andcorresponding to the second surface 1012), of the light guide member.This allows the general light guide member to provide surface-emittinglight from the entire emergent surface thereof as well.

In the general light guide member described above, however, the lightthat has entered the light guide member through the incident surfacethereof is repeatedly reflected a number of times from both surfacesalong the thickness of the light guide member and thereby guided to aportion, distant from the incident surface, of the light guide member.Therefore, the larger the number of times the light is totallyreflected, the more likely the condition for the total reflection (i.e.,angle of incidence≥critical angle) fails to be satisfied. This increasesthe chances of the light leaking out through one surface (correspondingto the first surface 1011) along the thickness of the light guidemember.

Particularly when an optical system including a light guide member isapplied to a head-up display to be installed in a moving vehicle B1 asin the display system 300 according to this embodiment, the light guidemember is required to provide a relatively narrow viewing angle and ahigh light intensity. That is to say, in the head-up display, theluminous intensity distribution of the light emerging from the lightguide member is suitably controlled according to the optical system1320, and therefore, a narrower viewing angle is required compared to ageneral light guide member for use in a backlight for a liquid crystaldisplay. It is difficult for the general light guide member to provide anarrower viewing angle. Thus, using the general light guide member in ahead-up display often allows the light to emerge in unwanted directionsas well.

In contrast, the optical system 1100 according to this embodimentincludes the light control members 1002 and the prisms 1003 as describedabove, and therefore, allows most of the light that has entered thelight guide member 1001 through the incident surface 1010 to travelalong the direct optical path L10. That is to say, according to thisembodiment, most of the light that has entered the light guide member1001 through the incident surface 1010 is directly incident on any ofthe prisms 1003 and allowed to emerge from the second surface 1012without being repeatedly totally reflected from the first surface 1011and the second surface 1012. Therefore, according to this embodiment,the condition for the total reflection rarely fails be satisfied,compared to the general light guide member. This reduces the chances ofthe light leaking out through the first surface 1011 and eventuallycontributes to increasing the light extraction efficiency. In addition,most of the light incident on the incident surface 1010 is parallelbeams. This reduces the chances of the light diverging, and therefore, arelatively narrow angle of emergence may be maintained even for thelight reflected from the prism 1003 and emerging from the second surface1012. Consequently, the optical system 1100 according to this embodimentallows most of the light incident through the incident surface 1010 toemerge at such a narrow angle and achieves a relatively high lightintensity by using the direct optical path L10.

In this embodiment, the light emerging from the second surface 1012after having traveled along the direct optical path L10 accounts for 50%or more of the light that has entered the light guide member 1001through the incident surface 1010. That is to say, part of the lightthat has entered the light guide member 1001 through the incidentsurface 1010 does not travel along the direct optical path L10. In thisembodiment, however, the majority (i.e., a half or more) of the lightincident through the incident surface 1010 emerges from the secondsurface 1012 after having traveled along the direct optical path L10.This makes the light extraction efficiency of the light guide member1001 at least equal to 50%. The light extraction efficiency of the lightguide member 1001 is more suitably equal to or greater than 70% and mayeven be 80% or more.

Increasing the light extraction efficiency of the light guide member1001 in this manner eliminates the need to provide a reflective sheet, aprism sheet, a dual brightness enhancement film (DBEF), a Fresnel lenssheet, or any other optical elements for the first surface 1011 of thelight guide member 1001. That is to say, this reduces the leakage of thelight from the first surface 1011, and therefore, a sufficiently highlight extraction efficiency is achievable even with none of theseoptical elements arranged on the first surface 1011 of the light guidemember 1001.

(2.4) Obliquely Incident Light

Next, a configuration for allowing incoming light to enter the lightguide member 1001 through the incident surface 1010 thereof will bedescribed in detail with reference to FIGS. 10A and 10B.

Specifically, in the optical system 1100 according to this embodiment,the optical axis Ax1 of the light incident through the incident surface1010 is tilted with respect to the first surface 1011 such that the gapdistance between the optical axis Ax1 and the first surface 1011 narrowsas the distance from the incident surface 1010 increases (i.e., as theincident light goes farther away from the incident surface 1010). Inparticular, in this embodiment, parallel light is incident from thelight control members 1002 onto the incident surface 1010 of the lightguide member 1001, and therefore, each of the light beams included inthe parallel light is tilted with respect to the first surface 1011.Moreover, in this embodiment, the first surface 1011 is a plane and thelight beams included in the parallel light that has been incident on theincident surface 1010 of the light guide member 1001 are tilted at thesame angle with respect to the first surface 1011.

Specifically, the first surface 1011 and the second surface 1012 are notparallel to each other but tilted with respect to each other. That is tosay, as described above, the second surface 1012 is a plane parallel tothe X-Y plane, while the first surface 1011 is a plane which is notparallel to, but tilted with respect to, the X-Y plane. In this case,the first surface 1011 is tilted with respect to the X-Y plane such thatas the distance from the incident surface 1010 increases, the firstsurface 1011 comes closer toward the second surface 1012. In short, thefirst surface 1011 and second surface 1012, i.e., both surfaces alongthe thickness, of the light guide member 1001 are tilted with respect toeach other. Thus, the thickness of the light guide member 1001 is notconstant but varies to gradually decrease in a certain direction. Inthis embodiment, the first surface 1011 is tilted with respect to thesecond surface 1012 such that as the distance from the incident surface1010 increases in the Y-axis direction, the first surface 1011 comescloser toward the second surface 1012. Therefore, the thickness of thelight guide member 1001 is the largest at the end portion thereof withthe incident surface 1010 and decreases gradually as the distance fromthe incident surface 1010 increases (i.e., as the distance to the endsurface 1013 decreases) in the Y-axis direction.

On the other hand, the light entering the light guide member 1001through the incident surface 1010 has been controlled by the lightcontrol members 1002 into parallel light parallel to the second surface1012. That is to say, the optical axis Ax1 of the light incident throughthe incident surface 1010 is parallel to the second surface 1012.Therefore, the optical axis Ax1 of the light incident through theincident surface 1010 is tilted at a predetermined tilt angle withrespect to the first surface 1011. The tilt angle of the incident lightis the same as the tilt angle defined by the first surface 1011 withrespect to the X-Y plane (i.e., the second surface 1012).

More specifically, each light control member 1002 includes a pathgenerating portion 1023 that forms paths L31, L32, L33 for the lightbetween its associated light source 1004 and the incident surface 10 asshown in FIG. 10A. The path generating portion 1023 extends along a linetilted with respect to the first surface 1011 (e.g., along the opticalaxis Ax1 in this example) when viewed from the incident surface 1010 andforms the paths L31, L32, L33 for the light between the light source1004 and the incident surface 10. That is to say, in this embodiment,the light control member 1002 is integrated with the light guide member1001.

In other words, the light control member 1002 includes a portion (i.e.,the path generating portion 1023) protruding along the optical axis Ax1that is tilted with respect to the first surface 1011 when viewed fromthe incident surface 1010 of the light guide member 1001. In addition,the light control member 1002 makes the path generating portion 1023form the path L31, L32, L33 for the light between the light source 1004and the incident surface 1010. Thus, the light emitted from the lightsource 1004 passes through the path generating portion 1023 of the lightcontrol member 1002 to be incident along the optical axis Ax1, which istilted with respect to the first surface 1011, onto the incident surface1010. That is to say, the light emitted from the light source 1004 isincident on the incident surface 1010 of the light guide member 1001after having passed through the inside of the light control member 1002(i.e., via the path generating portion 1023). The optical axis Ax1 ofthe light incident through the incident surface 1010 is tilted at apredetermined tilt angle with respect to the first surface 1011.

According to this configuration, the light entering the light guidemember 1001 through the incident surface 1010 travels inside the lightguide member 1001 to be obliquely incident on the first surface 1011. Inother words, the light entering the light guide member 1001 through theincident surface 1010 is intentionally directed toward the first surface1011. At this time, when the light beams are incident on the pluralityof prisms 1003 provided on the first surface 1011, the light beams arereflected from the respective reflective surfaces 1030 of the prisms1003 toward the second surface 1012 as shown in FIG. 10B. As a result,the light that has entered the light guide member 1001 through theincident surface 1010 travels along the direct optical path L10 toemerge from the second surface 1012.

As can be seen, the light incident through the incident surface 1010comes closer toward the first surface 1011 as the light goes fartheraway from the incident surface 1010 i.e., as the light travels deeperinside the light guide member 1001. This increases the chances of theincoming light being incident on the first surface 1011 (including theprisms 1003). In other words, most of the light incident through theincident surface 1010 is more likely to be incident on the first surface1011 before reaching the end surface 1013, facing the incident surface1010, of the light guide member 1001. In particular, intentionallydirecting the incoming light toward the first surface 1011 allows mostof the light incident through the incident surface 1010 to travel alongthe direct optical path L10 and emerge from the second surface 1012while reducing the dimension in the Y-axis direction of the light guidemember 1001. In other words, this enables the light to emergeefficiently from the second surface 1012 while reducing the leakage ofthe light from the end surface 1013. Consequently, this facilitatesincreasing the proportion of the light, traveling along the directoptical path L10 to emerge from the second surface 1012 out of the lightguide member 1001, to the light that has been incident through theincident surface 1010, thus contributing to increasing the lightextraction efficiency.

In addition, in this embodiment, the end surface 1013 is divided in theZ-axis direction into a sloped surface 1131 and a vertical surface 1132as shown in FIG. 10A. In other words, the end surface 1013 includes thesloped surface 1131 and the vertical surface 1132. The sloped surface1131 is a plane which is tilted with respect to the incident surface1010 such that the distance in the Y-axis direction from the incidentsurface 1010 is longer in a portion thereof adjacent to the secondsurface 1012 than in another portion thereof adjacent to the firstsurface 1011. On the other hand, the vertical surface 1132 is a planeparallel to the incident surface 1010. In this case, the sloped surface1131 is adjacent to the second surface 1012 and the vertical surface1132 is adjacent to the first surface 1011.

Providing the end surface 1013 with such a sloped surface 1131 allows,even if any part of the light incident through the incident surface 1010reaches the end surface 1013 without being incident on the first surface1011, such light to emerge from the second surface 1012. That is to say,if part of the light incident through the incident surface 1010 isincident on the sloped surface 1131 of the end surface 1013, the lightis totally reflected from the sloped surface 1131 toward the secondsurface 1012 and emerges from the second surface 1012. This enableseffectively extracting, from the second surface 1012, not only the lightemerging from the second surface 1012 out of the light guide member 1001after having traveled along the direct optical path L10 but also eventhe light that has reached the end surface 1013, thus contributing tofurther increasing the light extraction efficiency.

(2.5) Shape Transformation Function

Next, the shape transformation function of each light control member1002 will be described in detail with reference to FIG. 11 and FIGS.17A-20B.

Specifically, in the optical system 1100 according to this embodiment,each light control member 1002 has the shape transformation function oftransforming a shape projected onto a projection plane S1, which isparallel to an incident surface 1010, from a first shape F1 of the lightemitted from its associated light source 1004 into a second shape F2 ofthe light incident on the incident surface 1010 as shown in FIG. 11. InFIG. 11, the shape (first shape F1), projected onto the projection planeS1, of the light emitted from the light source 1004 and the shape(second shape F2), projected onto the projection plane S1, of the lightincident on the incident surface 1010 are schematically shown inballoons. As can be seen, the light control member 1002 according tothis embodiment has not only the function of substantially collimatingthe light emitted from the light source 1004 into parallel rays but alsothe shape transformation function, i.e., the function of transformingthe shape of the light projected onto the projection plane S1 (e.g., theincident surface 1010 in this embodiment).

The shape transformation function allows the light emitted from thelight source 1004 to have its shape projected onto the projection planeS1 transformed from the first shape F1 into the second shape F2 beforebeing incident on the incident surface 1010. The second shape F2 is ashape, to which the first shape F1 as its base shape has beentransformed by the shape transformation function and which is differentfrom the first shape F1. In this embodiment, for example, the firstshape F1 is a circle-based shape, while the second shape F2 is asquare-based shape, as shown in FIG. 11.

More specifically, the second shape F2 is formed by deforming thecircle-based first shape F1 such that the first shape F1 is turned intoa shape closer to a quadrangle by making at least one corner portion F21thereof protruding. That is to say, the shape formed by expanding thefirst shape F1 in four directions is the second shape F2. Such a shapetransformation function allows the first shape F1 to be approximated byan incircle of the second shape F2. Thus, the circumcircle of the secondshape F2 is larger than the circumcircle of the first shape F1.

In other words, the second shape F2 is formed by adding at least onecorner portion F21 to the first shape F1 to turn the first shape F1 intoa shape closer to a polygon. Such a shape transformation function allowslight, of which a projection (irradiation) area has the second shape F2which is less round than the first shape F1, to be incident on theincident surface 1010. That is to say, this allows the light to beincident on an area around a corner of the incident surface 1010 aswell, thus making the light incident more uniformly over the entireincident surface 1010.

In this embodiment, a plurality of light sources 1004 and a plurality oflight control members 1002 are provided as described above. Therefore,each of the plurality of light control members 1002 transforms, throughthe shape transformation function, the shape of the light that has comefrom its associated light source 1004 and is going to be incident on theincident surface 1010, thus allowing the light to be incident moreuniformly on the entire incident surface 1010. For example, if the lighthaving the circle-based first shape F1 is incident on the incidentsurface 1010, two light beams incident on the incident surface 1010 fromtwo adjacent light sources 1004 often leave a gap between themselves oroverlap with each other. On the other hand, making light beams havingthe square-based second shape F2 incident on the incident surface 1010reduces the chances of leaving such a gap or overlapping with each otherbetween the light beams that have been incident on the incident surface1010 from two adjacent light sources 1004.

Such a shape transformation function may be provided by, for example,the light control member 1002 having the following configuration.

Specifically, in this embodiment, the light control member 1002 (opticalmember 1020) includes an incident lens 1021 as shown in FIGS. 17A-17C.FIG. 17B is a cross-sectional view thereof taken along the plane B1-B1shown in FIG. 17A. FIG. 17C is a cross-sectional view thereof takenalong the plane C1-C1 shown in FIG. 17A.

The incident lens 1021 has a main incident surface 1211 and an auxiliaryincident surface 1212. The main incident surface 1211 is arranged toface the light source 1004. The auxiliary incident surface 1212 isarranged to face toward a normal L21 to the main incident surface 1211and located at least partially along a circumference of the mainincident surface 1211. The auxiliary incident surface 1212 may beparallel to (i.e., not tilted), or tilted with respect to, the normalL21 to the main incident surface 1211.

In this case, the incident lens 1021 allows the light emitted from thelight source 1004 to enter itself through the main incident surface 1211and the auxiliary incident surface 1212. Thus, at least part of thelight that has come from the light source 1004 is refracted, whilepassing through the incident lens 1021, by either the main incidentsurface 1211 or the auxiliary incident surface 1212 according to theangle of incidence defined by the light ray with respect to either themain incident surface 1211 or the auxiliary incident surface 1212. Inthis manner, the light control member 1002 refracts at least part of thelight incident on either the main incident surface 1211 or the auxiliaryincident surface 1212 to direct the incident light toward the incidentsurface 1010 of the light guide member 1001.

In addition, the light control member 1002 further has an outerperipheral surface 1213. The outer peripheral surface 1213 is locatedopposite from the normal L21 to the main incident surface 1211 withrespect to the auxiliary incident surface 1212. The outer peripheralsurface 1213 totally reflects, toward the incident surface 1010 of thelight guide member 1001, the light that has entered the light controlmember 1002 through the auxiliary incident surface 1212. That is to say,at least part of the light that has entered the light control member1002 through the auxiliary incident surface 1212 is totally reflectedfrom the outer peripheral surface 1213 and thereby directed toward theincident surface 1010 of the light guide member 1001.

The light control member 1002 has a plurality of lens surfaces 1201-1205on a counter surface thereof facing the light source 1004. As usedherein, the “counter surface,” i.e., a surface, facing the light source1004, of the light control member 1002 is one of the surfaces, arrangedface to face to the light source 1004, of the light control member 1002.In this embodiment, the counter surface, facing the light source 1004,of the light control member 1002 is defined by the incident lens 1021out of the light control member 1002. As described above, the incidentlens 1021 has the main incident surface 1211 and the auxiliary incidentsurface 1212. In this embodiment, the auxiliary incident surface 1212may be divided into the plurality of lens surfaces 1201-1205, forexample. The auxiliary incident surface 1212 is divided into theplurality (e.g., five in this example) of lens surfaces 1201-1205 alongthe circumference, defined around a counter axis with respect to thelight source 1004, of the light control member 1002. As used herein, the“counter axis” refers to a virtual axis extending in the direction inwhich the light control member 1002 faces the light source 1004. That isto say, the counter axis of the light control member 1002 with respectto the light source 1004 is a virtual axis extending from the lightcontrol member 1002 in a direction in which the light control member1002 and the light source 1004 face each other. In this embodiment, thecounter axis of the light control member 1002 with respect to the lightsource 1004 may be, for example, the normal L21 (see FIG. 11) to themain incident surface 1211.

The tilt angle defined by the counter surface, facing the light source1004, of the light control member 1002 with respect to the counter axisto the light source 1004 varies along the circumference defined aroundthe counter axis. Specifically, the counter surface (e.g., the incidentlens 1021 in this example), facing the light source 1004, of the lightcontrol member 1002 includes the plurality of lens surfaces 1201-1205 asdescribed above. The tilt angles defined by the plurality of lenssurfaces 1201-1205 with respect to the counter axis (e.g., the normalL21 in this example) are not constant along the circumference definedaround the counter axis. Specifically, the tilt angles defined by thelens surfaces 1202, 1204 with respect to the counter axis are largerthan the tilt angles defined by the lens surfaces 1201, 1203, 1205 withrespect to the counter axis. In other words, the lens surfaces 1202,1204 are configured to be tilted more significantly with respect to thenormal L21 than the lens surfaces 1201, 1203, 1205 are.

In addition, the counter surface, facing the light source 1004, of thelight control member 1002 has an asymmetric shape in one directionperpendicular to the counter axis (e.g., the normal L21 in this example)with respect to the light source 1004. In this embodiment, the incidentlens 1021, defining the counter surface, facing the light source 1004,of the light control member 1002, has an asymmetric shape in the Z-axisdirection. Specifically, when viewed from the main incident surface1211, the incident lens 1021 has the auxiliary incident surface 1212(including the lens surfaces 1202, 1203, 1204) only on one side in theZ-axis direction and is opened on the other side in the Z-axisdirection.

According to the configuration described above, the shape transformationfunction may be provided by the light control member 1002 and the rangein which the light that has entered the light guide member 1001 throughthe incident surface 1010 may reach inside the light guide member 1001may be controlled without depending on the first shape F1 that is theshape of the light emitted from the light source 1004.

FIGS. 18A-20B illustrate the results of comparison between the lightcontrol member 1002 of the optical system 1100 according to thisembodiment and a light control member 1002X according to a comparativeexample. In the light control member 1002X according to the comparativeexample, the auxiliary incident surface 1212 is not divided into theplurality of lens surfaces 1201-1205 but is a single continuous curvedsurface.

In FIGS. 18A-20B, the range that the light emitted from the light source1004 may reach is schematically indicated by shading (dots). In thiscase, there are three levels of shades, which are set according to theintensity of the light incident from the light source 1004.Specifically, the higher the intensity of the light incident from thelight source 1004 is, the darker the shade is. FIG. 20A illustrates alight intensity distribution (more exactly, illuminance distribution) onthe first surface 1011 as viewed from over the first surface 1011 alongthe thickness of the light guide member 1001 (i.e., Z-axis direction) ina situation where light has been directed from the light control member1002 according to this embodiment toward the light guide member 1001.FIG. 20B illustrates a light intensity distribution (more exactly,illuminance distribution) on the first surface 1011 as viewed from overthe first surface 1011 along the thickness of the light guide member1001 (i.e., Z-axis direction) in a situation where light has beendirected from the light control member 1002X according to a comparativeexample toward the light guide member 1001. FIGS. 20A and 20B eachillustrate the light intensity distribution (illuminance distribution)of the light that has been incident on the light guide member 1001 froma single light control member 1002, 1002X.

That is to say, in the light control member 1002 according to thisembodiment, the light emitted from the light source 1004 is incident onthe light control member 1002 through the incident lens 1021 and spreadin a relatively broad range inside the light control member 1002 asshown in FIGS. 18A and 19A. In particular, according to the shapetransformation function of the light control member 1002, the shape ofthe light projected onto the projection plane S1 (incident surface 1010)is transformed from the circle-based first shape F1 (see FIG. 11) intothe square-based second shape F2 (see FIG. 11). Specifically, the lightincident on the lens surface 1202, 1204 reaches, when viewed from oneend of an extension of the normal L21 to the main incident surface 1211,a region more distant from the normal L21 than the light incident on thelens surface 1201, 1203, 1205 does. That is to say, the lens surface1202, 1204 defines a larger tilt angle with respect to the counter axis(e.g., the normal L21 in this example) than the lens surface 1201, 1203,1205 does. Thus, the light ray incident on the lens surface 1202, 1204is refracted to define a larger tilt angle with respect to the normalL21. As a result, the light incident through the lens surface 1202, 1204out of the auxiliary incident surface 1212 may reach as far as thecorners of the light control member 1002.

Meanwhile, in the light control member 1002X according to thecomparative example, the light emitted from the light source 1004 entersthe light control member 1002X through the incident lens 1021 but staysin a relatively narrow range inside the light control member 1002X asshown in FIGS. 18B and 19B. Specifically, the light incident through theauxiliary incident surface 1212 spreads uniformly as viewed from one endof the extension of the normal L21 to the main incident surface 1211 andmay reach only a certain range from the normal L21. As a result, thelight incident through the auxiliary incident surface 1212 cannot reachas far as the corners of the light control member 1002X, and therefore,the range that the light may reach as viewed from one end of theextension of the normal L21 to the main incident surface 1211 isnarrower than the light control member 1002 according to thisembodiment.

Thus, the light control member 1002 according to this embodiment allowsthe light incident through the incident surface 1010 to spread in arelatively broad range inside the light guide member 1001 as shown inFIG. 20A. Meanwhile, the light control member 1002X according to thecomparative example allows the light incident through the incidentsurface 1010 to reach a relatively narrow range inside the light guidemember 1001 as shown in FIG. 20B. More specifically, the light controlmember 1002 according to this embodiment allows the light to reach agenerally rectangular area when viewed from one end along the thicknessof the light guide member 1001 (in the Z-axis direction) as shown inFIG. 20A. Meanwhile, the light control member 1002X according to thecomparative example allows the light to reach a generally ellipticalarea when viewed from one end along the thickness of the light guidemember 1001 (in the Z-axis direction) as shown in FIG. 20B.Consequently, in a situation where light enters the light guide member1001 through a plurality of light control members 1002, this embodimentallows the light to reach the entire first surface 1011 more easily andallows the light to be extracted from the entire second surface 1012more uniformly, than the comparative example.

(2.6) Asymmetric Shape

Next, the asymmetric shape of the light control member 1002 will bedescribed in detail with reference to FIG. 11 and FIGS. 21A-21C.

Specifically, an optical member 1020 for use as the light control member1002 in the optical system 1100 according to this embodiment includesthe incident lens 1021 and an outlet portion 1022 as shown in FIG. 11.The optical member 1020 allows the light that has been incident on theincident lens 1021 from the light source 1004 to go out of the opticalmember 1020 itself from the outlet portion 1022. The incident lens 1021has the main incident surface 1211 and the auxiliary incident surface1212. The main incident surface 1211 is arranged to face the lightsource 1004. The auxiliary incident surface 1212 is directed toward thenormal L21 to the main incident surface 1211 and located at leastpartially along the circumference of the main incident surface 1211. Anoptical axis Ax2 of the light source 1004 is tilted with respect to anormal L21 to the main incident surface 1211.

In the example shown in FIG. 11, the optical axis Ax2 of the lightsource 1004 is tilted toward the first surface 1011 by a tilt angle θ2with respect to the normal L21 to the main incident surface 1211 whenviewed from one end in the X-axis direction. In this case, the opticalaxis Ax2 of the light source 1004 and the normal L21 to the mainincident surface 1211 are both parallel to a Y-Z plane. As used herein,the “Y-Z plane” refers to a plane including the Y-axis and the Z-axisand perpendicular to the X-axis. In other words, the optical axis Ax2 ofthe light source 1004 and the normal L21 to the main incident surface1211 are both perpendicular to the X-axis.

More specifically, the optical axis Ax2 of the light source 1004 and thenormal L21 to the main incident surface 1211 intersect with each otheron the surface (light-emitting surface) of the light source 1004. Inother words, the light source 1004 is arranged such that the centerpoint of the light-emitting surface thereof is located on the normal L21to the main incident surface 1211. Besides being arranged in thismanner, the light source 1004 is also held to be tilted toward the firstsurface 1011 by the tilt angle θ2. This allows the light emitted fromthe light source 1004 to be incident onto the incident lens 1021 of theoptical member 1020 asymmetrically with respect to the normal L21 to themain incident surface 1211.

Seeing things from another perspective, the light source 1004 hasdirectivity. The light emitted from the light source 1004 has intensitythat changes according to the direction as viewed from the light source1004. For example, if the intensity of each light ray emitted from thelight source 1004 is expressed by percentage with respect to the maximumintensity of a light ray emitted from the light source 1004 that issupposed to be 100%, then the light emitted from the light source 1004includes light rays with various intensities such as 10%, 20%, and 30%.In the following description, a light ray on the optical axis Ax2 of thelight source 1004 is supposed to have the maximum intensity (i.e., anintensity of 100%) and the intensity of a light ray is supposed todecrease as the angle defined with respect to the optical axis Ax2increases.

The light rays that have been incident on the incident lens 1021 fromthe light source 1004 include a principal ray L11, a first auxiliary rayL12, and a second auxiliary ray L13 as shown in FIG. 21A. Both the firstauxiliary ray L12 and the second auxiliary ray L13 have a lowerintensity than the principal ray L11. The principal ray L11, the firstauxiliary ray L12, and the second auxiliary ray L13 are arranged in thisorder in a direction perpendicular to the normal L21 to the mainincident surface 1211. The first auxiliary ray L12 and the secondauxiliary ray L13 may have a lower intensity than the principal ray L11.For example, if the principal ray L11 has an intensity of 90%, then thefirst auxiliary ray L12 and the second auxiliary ray L13 may each havean intensity less than 90%. The first auxiliary ray L12 and the secondauxiliary ray L13 may have the same intensity or mutually differentintensities, whichever is appropriate.

Specifically, these light rays are arranged in the order of theprincipal ray L11, the first auxiliary ray L12, and the second auxiliaryray L13 from the first surface 1011 (i.e., from bottom to top in FIG.21A) in the Z-axis direction perpendicular to the normal L21 to the mainincident surface 1211. That is to say, the principal ray L11, the firstauxiliary ray L12, and the second auxiliary ray L13 are arranged fromthe first surface 1011 in the descending order of their intensities.

In this embodiment, the intensity of the principal ray L11 is themaximum intensity among the light rays that have been incident on theincident lens 1021 from the light source 1004. That is to say, theintensity of the principal ray L11 is 100%. On the other hand, theintensities of the first auxiliary ray L12 and the second auxiliary rayL13 are both less than 100%. In this embodiment, the intensities of thefirst auxiliary ray L12 and the second auxiliary ray L13 are bothsupposed to be 70% as an example. That is to say, the first auxiliaryray L12 and the second auxiliary ray L13 have the same intensity.

Meanwhile, the light rays emitted from the light source 1004 include notonly the principal ray L11, the first auxiliary ray L12, and the secondauxiliary ray L13 but also a third auxiliary ray L14 and a fourthauxiliary ray L15 as well as shown in FIG. 21A. The third auxiliary rayL14 and the fourth auxiliary ray L15 each have a lower intensity thanthe first auxiliary ray L12 and the second auxiliary ray L13. The thirdauxiliary ray L14 and the fourth auxiliary ray L15 may have the sameintensity or mutually different intensities, whichever is appropriate.In this embodiment, the intensities of the third auxiliary ray L14 andthe fourth auxiliary ray L15 are both supposed to be 10% as an example.That is to say, the third auxiliary ray L14 and the fourth auxiliary rayL15 have the same intensity.

In the example illustrated in FIG. 21A, neither the third auxiliary rayL14 nor the fourth auxiliary ray L15 is incident on the optical member1020. That is to say, neither the third auxiliary ray L14 nor the fourthauxiliary ray L15 reaches the incident surface 1010 of the light guidemember 1001. Nevertheless, the third auxiliary ray L14 and the fourthauxiliary ray L15 have a much lower intensity than the principal rayL11, the first auxiliary ray L12, and the second auxiliary ray L13, andtherefore, the loss caused by their failure to reach the incidentsurface 1010 is insignificant.

In addition, in this embodiment, the principal ray L11 is also incidenton the auxiliary incident surface 1212. That is to say, the principalray L11 is incident on the auxiliary incident surface 1212, out of themain incident surface 1211 and the auxiliary incident surface 1212 ofthe incident lens 1021. The principal ray L11 incident on the auxiliaryincident surface 1212 is refracted by the auxiliary incident surface1212 and totally reflected by the outer peripheral surface 1213 towardthe incident surface 1010 as shown in FIG. 21A. As a result, theprincipal ray L11 is directed toward the incident surface 1010 via theoutlet portion 1022.

In addition, the auxiliary incident surface 1212 has an asymmetric shapewith respect to the normal L21 to the main incident surface 1211. Inthis embodiment, the incident lens 1021 has an asymmetric shape in theZ-axis direction. Specifically, the incident lens 1021 has the auxiliaryincident surface 1212 (including the lens surfaces 1202, 1203, 1204)only on one side in the Z-axis direction and is opened on the other sidein the Z-axis direction as viewed from the main incident surface 1211.

That is to say, light rays with relatively high intensities, includingthe principal ray L11, the first auxiliary ray L12, and the secondauxiliary ray L13, are concentrated toward the first surface 1011 (i.e.,the lower part in FIG. 21A) of the optical member 1020 (light controlmember 1002) as viewed from the normal L21 to the main incident surface1211. Thus, adopting an asymmetric shape in which the incident lens 1021is aggregated in only such a part where the light rays with relativelyhigh intensities are concentrated and in which the opposite part (i.e.,the upper part in FIG. 21A) is simplified for the optical member 1020(light control member 1002) allows the dimension t1 in the Z-axisdirection to be reduced easily.

On the other hand, FIG. 21B illustrates, as a comparative example, anoptical system 1100Y including an optical member 1020Y and anillumination system 1200Y including the optical system 1100Y. In theillumination system 1200Y according to this comparative example, theoptical member 1020Y has a symmetric shape, in the Z-axis direction,with respect to the normal L21 to the main incident surface 1211.Specifically, the optical member 1020Y is formed by adopting, for theopposite part (i.e., the upper part in FIG. 21A), a configurationsymmetric to that of the part closer to the first surface 1011 (i.e.,the lower part shown in FIG. 21A) of the optical member 1020 accordingto this embodiment as viewed from the normal L21 to the main incidentsurface 1211.

Furthermore, in the illumination system 1200Y according to thecomparative example, the optical axis Ax2 of the light source 1004 islocated on the normal L21 to the main incident surface 1211. That is tosay, in the comparative example, the optical axis Ax2 of the lightsource 1004 is parallel to the normal L21 to the main incident surface1211.

In such a comparative example, the principal ray L11 is located on theoptical axis Ax2 of the light source 1004 as shown in FIG. 21B. Inaddition, in the Z-axis direction, the third auxiliary ray L14 and thefourth auxiliary ray L15 are located on both sides of the principal rayL11, and the first auxiliary ray L12 and the second auxiliary ray L13are located on both sides of the third auxiliary ray L14 and the fourthauxiliary ray L15, respectively. As a result, in the illumination system1200Y according to this comparative example, light rays with relativelyhigh intensities, including the principal ray L11, the first auxiliaryray L12, and the second auxiliary ray L13, are all incident on theincident surface 1010 of the light guide member 1001. Nevertheless, theoptical member 1020Y according to this comparative example adopts such ashape that is symmetric in the Z-axis direction, and therefore, itsdimension t2 in the Z-axis direction is larger than the dimension t1 ofthe optical member 1020 according to this embodiment.

On the other hand, FIG. 21C illustrates, as another comparative example,an optical system 1100Z including a different optical member 1020Z andan illumination system 1200Z including such an optical system 1100Z. Inthe illumination system 1200Z according to this comparative example, theoptical member 1020Z has a smaller dimension in the Z-axis directionthan the optical member 1020Y according to the comparative example byremoving both end portions thereof in the Z-axis direction. Thedimension t3 in the Z-axis direction of this optical member 1020Z is thesame as the dimension t1 of the optical member 1020 according to thisembodiment.

Furthermore, in the illumination system 1200Z according to thiscomparative example, the optical axis Ax2 of the light source 1004 islocated on the normal L21 to the main incident surface 1211. That is tosay, in this comparative example, the optical axis Ax2 of the lightsource 1004 is parallel to the normal L21 to the main incident surface1211.

In such a comparative example, the principal ray L11 is located on theoptical axis Ax2 of the light source 1004 as shown in FIG. 21C. Inaddition, the third auxiliary ray L14 and the fourth auxiliary ray L15are located on both sides of the principal ray L11 in the Z-axisdirection. Nevertheless, the first auxiliary ray L12 and the secondauxiliary ray L13 will leak out of the optical member 1020Z and fail tobe incident on the incident surface 1010 of the light guide member 1001.As a result, in the illumination system 1200Z according to thiscomparative example, light rays with relatively high intensities,including the first auxiliary ray L12 and the second auxiliary ray L13,are not incident on the incident surface 1010 of the light guide member1001, thus resulting a much lower light extraction efficiency than thisembodiment.

As can be seen from the foregoing description, the optical member 1020according to this embodiment contributes to increasing the lightharvesting efficiency thereof while reducing its overall size, comparedto the comparative examples shown in FIGS. 21B and 21C.

(2.7) Luminous Intensity Distribution Control Member

Next, the luminous intensity distribution control member 1014 will bedescribed in detail with reference to FIG. 12.

Specifically, in this embodiment, at least one of the first surface 1011or the second surface 1012, 1012A includes the luminous intensitydistribution control member 1014. The luminous intensity distributioncontrol member 1014 controls a luminous intensity distribution of thelight extracted from the second surface 1012, which is a light emergentsurface. In this embodiment, the luminous intensity distribution controlmember 1014 may be provided for the second surface 1012, for example. Inaddition, in this embodiment, the luminous intensity distributioncontrol member 1014 is formed integrally with the light guide member1001 and provided as an integrally molded product. That is to say, inthis embodiment, the light guide member 1001 and the luminous intensitydistribution control member 1014 form an integrally molded product andare inseparable from each other.

In short, in this embodiment, the light guide member 1001 includes thedirect optical path L10 that allows the light that has entered the lightguide member 1001 through the incident surface 1010 to be reflected onlyonce from the prism 1003 inside the light guide member 1001 beforeemerging from the second surface 1012 out of the light guide member1001. Thus, the shapes of the first surface 1011 and the second surface1012 do not contribute to guiding the light inside the light guidemember 1001. Therefore, even if the luminous intensity distributioncontrol member 1014 is provided on the first surface 1011 or the secondsurface 1012, the light guiding performance of the light guide member1001 hardly deteriorates.

Specifically, the luminous intensity distribution control member 1014according to this embodiment includes a lens. That is to say, theluminous intensity distribution control member 1014 has the function ofa lens serving as an optical element that causes incoming light toeither diverge or converge by refracting the light. This allows theluminous intensity distribution control member 1014 to control theluminous intensity distribution of the light extracted from the secondsurface 1012 as an emergent surface by causing the light to eitherdiverge or converge by refracting the light.

More specifically, the luminous intensity distribution control member1014 includes a multi-lens as a group of a plurality of small lenses1141. In this embodiment, each of the plurality of small lenses 1141 isconfigured in a semicircular columnar shape. The plurality of such smalllenses 1141 are arranged side by side in the X-axis direction. In thisembodiment, the plurality of small lenses 1141 are formed to cover theentire second surface 1012 with no gaps left between themselves. Themulti-lens having such a shape as a group of a plurality of small lenses1141 constitutes a so-called “cylindrical lens.”

(3) Variations

Note that the second embodiment described above is only an exemplary oneof various embodiments of the present disclosure and should not beconstrued as limiting. Rather, the second embodiment may be readilymodified in various manners depending on a design choice or any otherfactor without departing from the scope of the present disclosure. Thedrawings referred to in the foregoing description of the secondembodiment are all schematic representations. That is to say, the ratioof the dimensions (including thicknesses) of respective constituentelements illustrated on the drawings does not always reflect theiractual dimensional ratio.

Next, variations of the second embodiment will be enumerated one afteranother. Note that any the variations to be described below may beadopted as appropriate in combination with the second embodimentdescribed above.

(3.1) First Variation

In an optical system 1100A according to a first variation, the tiltangle θ3 defined by a reflective surface 1030 of a prism 1003A withrespect to the first surface 1011 is different from the optical system1100 according to the second embodiment as shown in FIGS. 22A-22C.

Specifically, the tilt angle θ3 defined by the reflective surface 1030of the prism 1003A with respect to the first surface 1011 is smallerthan the maximum angle of reflection when the light incident through theincident surface 1010 is totally reflected toward the second surface1012 by the direct optical path L10 as shown in FIG. 22B. In otherwords, the tilt angle θ3 of the reflective surface 1030 of the prism1003A according to this variation is smaller than the tilt angle θ1 ofthe reflective surface 1030 of the prism 1003 according to the secondembodiment (see FIG. 10B). This reduces, even if the angle of incidenceθ4 of the light incident on the reflective surface 1030 varies to acertain degree, the chances of the angle of incidence θ4 being smallerthan a critical angle. That is to say, this increases, even if the angleof incidence θ4 of the light incident on the reflective surface 1030varies to a certain degree, the chances of the light incident on thereflective surface 1030 being totally reflected from the reflectivesurface 1030. As a result, this reduces the light transmitted throughthe reflective surface 1030 and leaking out of the light guide member1001, thus contributing to increasing the light extraction efficiency.

Nevertheless, according to this variation, the light ray incident on thesecond surface 1012 after having traveled along the direct optical pathL10 follows an optical path tilted with respect to the Z-axis. As aresult, the light emerging from the second surface 1012 is notperpendicular to the second surface 1012 (i.e., does not travel in theZ-axis direction) but tilted with respect to a normal to the secondsurface 1012 as shown in FIG. 22A.

Thus, the normal L22 to the second surface 1012A may be tilted as shownin FIG. 22C with respect to the optical axis of the light incident onthe second surface 1012A after having traveled along the direct opticalpath L10. In the example illustrated in FIG. 22C, the second surface1012A is a plane not parallel to, but tilted by the angle θ5 withrespect to, the X-Y plane. In this case, the second surface 1012A istilted with respect to the X-Y plane to come closer toward the firstsurface 1011 as the distance from the incident surface 1010 increases.This makes the normal L22 to the second surface 1012A tilted withrespect to the optical axis of the light incident on the second surface1012A after having traveled along the direct optical path L10. Thiscauses the light ray incident on the second surface 1012A after havingtraveled along the direct optical path L10 to be refracted by the secondsurface 1012A and emerge in a direction perpendicular to the X-Y plane.That is to say, the light incident on the second surface 1012A at theangle of incidence θ6 emerges from the second surface 1012A at an angleof emergence θ7 (>θ6).

(3.2) Second Variation

In an optical system 1100B according to a second variation, the lightcontrol member 1002B thereof is tilted in its entirety with respect tothe light guide member 1001 as shown in FIGS. 23A and 23B, which is amajor difference from the optical system 1100 according to the secondembodiment.

Specifically, to provide the configuration that has been described inthe “(2.4) Obliquely incident light” section, the optical axis Ax1 ofthe light entering the light guide member 1001 through the incidentsurface 1010 may be tilted with respect to the first surface 1011 suchthat the gap distance between the optical axis Ax1 and the first surface1011 narrows as the distance from the incident surface 1010 increases.According to this variation, both surfaces along the thickness (i.e., inthe Z-axis direction) of the light control member 1002B are tilted withrespect to the light guide member 1001, thus making the light controlmember 1002B tilted in its entirety with respect to light guide member1001. Even such a configuration may also contribute to increasing theproportion of the light emerging from the second surface 1012 out of thelight guide member 1001 after having traveled along the direct opticalpath L10 with respect to the light incident through the incident surface1010, thus contributing to increasing the light extraction efficiency.

In particular, according to this variation, the optical axis Ax1 of thelight entering the light guide member 1001 through the incident surface1010 is tilted with respect to not only the first surface 1011 but alsothe second surface 1012 as shown in FIG. 23B. In this case, the opticalaxis Ax1 is tilted with respect to the second surface 1012 such that thegap distance between the optical axis Ax1 and the second surface 1012widens as the distance from the incident surface 1010 increases. Makingthe optical axis Ax1 tilted with respect to the second surface 1012 inthis manner reduces the chances of the light incident on the incidentsurface 1010 reaching an end surface 1013 as shown in FIG. 23B. As aresult, this allows the light to efficiently emerge from the secondsurface 1012 while reducing the leakage of light from the end surface1013.

In addition, in this variation, the light does not emerge from thesecond surface 1012 perpendicularly to the second surface 1012 (i.e.,does not travel in the Z-axis direction) but emerges obliquely to anormal to the second surface 1012 as shown in FIG. 23B. That is to say,in this variation, the light ray incident on the second surface 1012after having traveled along the direct optical path L10 follows theoptical path tilted with respect to the Z-axis as in the first variationshown in FIG. 22A, and therefore, is incident obliquely onto the secondsurface 1012.

As can be seen, the light emerging from the second surface 1012 afterhaving traveled along the direct optical path L10 does not have to beperpendicular to the second surface 1012 but may be tilted to anappropriate degree with respect to a normal to the second surface 1012.Furthermore, the direction of the light emerging from the second surface1012 after having traveled along the direct optical path L10 may or maynot be uniform over the entire second surface 1012. If the direction ofthe light emerging from the second surface 1012 is not uniform over theentire second surface 1012, then the light will emerge in a differentdirection from one area of the second surface 1012 to another.

Particularly when the optical system 1100B including the light guidemember 1001 is applied to a head-up display to be installed in a movingvehicle B1, the luminous intensity distribution of the light emergingfrom the light guide member 1001 is suitably controlled according to theoptical system 1320 as described above. In other words, the lightemerging from the optical system 1100B is suitably spread within therange of the light incident on the optical system 1320 according to thetype of the optical system 1320. That is to say, the emergent lightsuitably has a narrow viewing angle (i.e., has a high degree ofdirectivity) in each part of the second surface 1012 that is theemergent surface of the light guide member 1001 according to the type ofthe optical system 1320. Meanwhile, the direction of the emergent lightsuitably varies according to the type of the optical system 1320 fromone area of the second surface 1012 that is an emergent surface of thelight guide member 1001 to another.

Nevertheless, this does not mean that the light emerging from the secondsurface 1012 after having traveled along the direct optical path L10 istilted with respect to a normal to the second surface 1012 on thepremise that the optical axis Ax1 is tilted with respect to the secondsurface 1012. That is to say, even when the optical axis Ax1 is parallelto the second surface 1012 as in the second embodiment, the lightemerging from the second surface 1012 after having traveled along thedirect optical path L10 may also be tilted to an appropriate degree withrespect to the normal to the second surface 1012. Conversely, even whenthe optical axis Ax1 is tilted with respect to the second surface 1012,the light emerging from the second surface 1012 after having traveledalong the direct optical path L10 may also be perpendicular to thesecond surface 1012.

(3.3) Third Variation

A light control member 1002C according to a third variation has asymmetric shape in the thickness direction (Z-axis direction) as shownin FIG. 24, which is a major difference from the optical system 1100according to the second embodiment.

Specifically, in this variation, a counter surface, facing the lightsource 1004, of the light control member 1002C has a shape symmetric inone direction (Z-axis direction) perpendicular to the counter axis(e.g., the normal L21 to the main incident surface 1211 in thisvariation) with respect to the light source 1004. That is to say, theincident lens 1021, defining the counter surface, facing the lightsource 1004, of the light control member 1002C has a symmetric shape.Specifically, the incident lens 1021 has an auxiliary incident surface1212 along the entire circumference of the main incident surface 1211.The auxiliary incident surface 1212 is divided into a plurality of(e.g., eight in this variation) lens surfaces 1201-1208.

(3.4) Fourth Variation

In an illumination system 1200 including the optical system 1100according to a fourth variation, the illumination system 1200 isarranged parallel to the display 1005 as shown in FIGS. 25A and 25B,which is a major difference from the illumination system 1200 accordingto the second embodiment.

Specifically, in this variation, the second surface 1012, serving as theemergent surface of the illumination system 1200, of the light guidemember 1001 is arranged parallel to the back surface of the display1005. Nevertheless, in such an arrangement, the second surface 1012 istilted with respect to a horizontal plane. Thus, the light emergingstraight from the second surface 1012 will emerge obliquely upward fromthe image display unit 1310 as shown in FIG. 25A. Thus, the shape of theluminous intensity distribution control member 1014 provided for thesecond surface 1012 is suitably changed as shown in FIG. 25B to allowthe luminous intensity distribution control member 1014 to control theluminous intensity distribution of the light emerging from the secondsurface 1012. That is to say, the luminous intensity distributioncontrol member 1014 shown in FIG. 25B allows the light emerging from thesecond surface 1012 to go straight upward from the image display unit1310.

(3.5) Fifth Variation

In an optical system 1100 according to a fifth variation, a luminousintensity distribution control member 1014A (or 1014B) has a differentconfiguration as shown in FIGS. 26A and 26B from the counterpart of theoptical system 1100 according to the second embodiment.

In the example shown in FIG. 26A, the luminous intensity distributioncontrol member 1014A includes a lens array. As used herein, the lensarray refers to a type of multi-lens as a group of multiple smalllenses. In the luminous intensity distribution control member 1014A, aplurality of small lenses are arranged in matrix such that a pluralityof small lenses are arranged both vertically (i.e., in the Y-axisdirection) and horizontally (in the X-axis direction) on the secondsurface 1012. Each of the plurality of small lenses may be either aconvex lens or a concave lens, whichever is appropriate.

In the example shown in FIG. 26B, the luminous intensity distributioncontrol member 1014B includes a Fresnel lens. As used herein, theFresnel lens refers to a lens, of which the height of the protrusion (orthe depth of the recess) is reduced to a low level by dividing a singlelens into a plurality of concentric regions. In this variation, theluminous intensity distribution control member 1014B is configured as aFresnel lens formed by dividing a convex lens into a plurality ofconcentric regions around the center of the second surface 1012.

(3.6) Sixth Variation

In an optical system 1100 according to a sixth variation, the prism1003B, 1003C, 1003D, 1003E, 1003F, 1003G has a different shape as shownin FIGS. 27A-29B from its counterpart of the optical system 1100according to the second embodiment.

In the example shown in FIG. 27A, the plurality of prisms 1003B arearranged side by side to draw an arc-shaped curve when viewed from oneend in the Z direction. In this variation, the plurality of prisms 1003Bare arranged to draw an arc-shaped curve, which is convex in thedirection pointing away from the incident surface 1010. That is to say,in this variation, at least some of the prisms 1003B are tilted withrespect to the incident surface 1010 when viewed in the direction inwhich the first surface 1011 and the second surface 1012 are arrangedone on top of the other (i.e., in the Z-axis direction).

In the example shown in FIG. 27B, a plurality of prisms 1003C includedin even-numbered banks and a plurality of prisms 1003C included inodd-numbered banks are arranged such that their longitudinal ends (i.e.,their ends in the X-axis direction) do not overlap with each other inthe Y-axis direction. According to such an arrangement, when viewed fromthe incident surface 1010, the plurality of prisms 1003C are arrangedwith a narrow gap left between themselves in the X-axis direction.Optionally, the plurality of prisms 1003C arranged in this pattern mayalso be arranged to draw an arc-shaped curve when viewed from one end inthe Z-axis direction as in the example shown in FIG. 27A.

In the example shown in FIG. 28A, the plurality of prisms 1003D arearranged to form straight lines parallel to the X-axis when viewed fromone end in the Z-axis direction. In the example shown in FIG. 28A, theplurality of prisms 1003D are arranged on the first surface 1011 of thelight guide member 1001 to be spaced apart from each other in the Y-axisdirection. That is to say, in the example shown in FIG. 28A, theplurality of prisms 1003D are arranged side by side in the direction inwhich light is incident on the incident surface 1010 (i.e., in theY-axis direction).

In the example shown in FIG. 28B, the plurality of prisms 1003E arearranged to form arc-shaped curves when viewed from one end in theZ-axis direction. In this example, the plurality of prisms 1003E arearranged in an arc-shaped pattern which is convex in the directionpointing away from the incident surface 1010. In the example shown inFIG. 28B, the plurality of prisms 1003E are arranged on the firstsurface 1011 of the light guide member 1001 to be spaced apart from eachother in the Y-axis direction. That is to say, in the example shown inFIG. 28B, the plurality of prisms 1003E are arranged side by side in thedirection in which light is incident on the incident surface 1010 (i.e.,in the Y-axis direction).

In the example shown in FIG. 29A, a plurality of prisms 1003F includedin even-numbered banks and a plurality of prisms 1003F included inodd-numbered banks are arranged such that their longitudinal ends (i.e.,their ends in the X-axis direction) do not overlap with each other inthe Y-axis direction. In addition, the plurality of prisms 1003F arearranged to form free-form curves when viewed from one end in the Z-axisdirection. As used herein, examples of the “free-form curves” includevarious free-form curves such as C-, U-, J-, and S-curves. In thisvariation, the plurality of prisms 1003F are arranged to draw free-formcurves, which are convex in the direction pointing away from theincident surface 1010. That is to say, in this variation, at least someof the prisms 1003F are tilted with respect to the incident surface 1010when viewed in the direction in which the first surface 1011 and thesecond surface 1012 are arranged one on top of the other (i.e., in theZ-axis direction).

In the example shown in FIG. 29B, a plurality of prisms 1003G are alsoarranged as in the example shown in FIG. 29A to form free-form curveswhen viewed from one end in the Z-axis direction. In this variation, theplurality of prisms 1003G are arranged to draw free-form curves, whichare convex in the direction pointing toward the incident surface 1010.That is to say, in this variation, at least some of the prisms 1003G aretilted with respect to the incident surface 1010 when viewed in thedirection in which the first surface 1011 and the second surface 1012are arranged one on top of the other (i.e., in the Z-axis direction).

In order for an optical system to achieve a narrow viewing angle, theoptical path of the light emerging from the second surface 1012 ispreferably as nearly perpendicular to the second surface 1012 aspossible. In this case, the light emitted from the light source 1004 hasits divergence angle narrowed by the light control member 1002.Nevertheless, in an X-Y plane, not all the light incident on theincident surface 1010 travels along such an optical path perpendicularto the incident surface 1010 but some of the light travels along anoptical path that spreads in the X-axis direction. Therefore, if theprism 1003 is arranged in a straight line parallel to the X-axis, thenpart of the light incident on the incident surface 1010 will be incidentobliquely onto the reflective surface 1030 of the prism 1003 in the X-Yplane. In that case, the light totally reflected from the reflectivesurface 1030 of the prism 1003 travels along an optical path angled withrespect to the second surface 1012, not the optical path perpendicularto the second surface 1012. This may reduce the chances of achieving anarrow viewing angle.

On the other hand, in the variations shown in FIGS. 27A, 28B, 29A, and29B, at least some of the prisms 1003B, 1003E, 1003F, 1003G are tiltedwith respect to the incident surface 1010 when viewed in the Z-axisdirection. That is to say, these variations increase the chances of thelight incident on the incident surface 1010 being incidentperpendicularly to the reflective surface 1030 of the prisms 1003B,1003E, 1003F, 1003G within the X-Y plane. Thus, these variationsincrease the chances of the light totally reflected from the reflectivesurface 1030 of the prisms 1003B, 1003E, 1003F, 1003G traveling along anoptical path perpendicular to the second surface 1012. Consequently,these variations have the advantage of achieving a narrow viewing anglemore easily.

Alternatively, in the variation shown in FIG. 27A, the plurality ofprisms 1003B may also be arranged to form arc-shaped curves which areconvex in the direction pointing toward the incident surface 1010.Likewise, in the variation shown in FIG. 28B, the plurality of prisms1003E may also be arranged to form arc-shaped curves which are convex inthe direction pointing toward the incident surface 1010. Furthermore,the plurality of prisms 1003F, 1003G arranged to form free-form curvesas shown in FIGS. 29A and 29B as viewed from one end in the Z-axisdirection may also have a shape continuous along their longitudinal axisas shown in FIG. 28B.

(3.7) Seventh Variation

In an optical system 1100 according to a seventh variation, the prism1003H, 1003I, 1003J has a different cross-sectional shape as shown inFIGS. 30A-30C from the counterpart of the optical system 1100 accordingto the second embodiment. FIGS. 30A-30C are schematic representationscorresponding to FIG. 10B illustrating, on a larger scale, a principalpart (the region A1 shown in FIG. 10A) of the optical system 1100.

In the example illustrated in FIG. 30A, the reflective surface 1030 ofthe prism 1003H is formed as a curved surface, not a flat surface. Inthe example illustrated in FIG. 30A, the reflective surface 1030 of theprism 1003H is a convex curved surface which is convex in a directionpointing away from the second surface 1012 (i.e., away from the incidentsurface 1010) when viewed from one end in the X-axis direction. In thiscase, the reflective surface 1030 of the prism 1003H is curved only on across section parallel to a Y-Z plane (i.e., only on a cross sectionperpendicular to the X-axis) but is linear on a cross section parallelto a X-Y plane (i.e., on a cross section perpendicular to the Z-axis).However, the example shown in FIG. 30A is only an example and should notbe construed as limiting. Alternatively, the reflective surface 1030 ofthe prism 1003H may also be a concave curved surface which is curved tobe convex toward the second surface 1012 (i.e., toward the incidentsurface 1010) when viewed from one end in the X-axis direction.Furthermore, the reflective surface 1030 of the prism 1003H may becurved only on a cross section parallel to the X-Y plane (i.e., only ona cross section perpendicular to the Z-axis) or may be curved both on across section parallel to the Y-Z plane and on a cross section parallelto the X-Y plane.

Meanwhile, in the example illustrated in FIG. 30B, the reflectivesurface 1030 of the prism 1003I is formed as a polygonal surface, not aflat surface. As used herein, the “polygonal surface” refers to asurface formed as a combination of a plurality of planes with differentorientations to define some surfaces of a polyhedron and is a so-called“flexed surface.” In the example illustrated in FIG. 30B, the reflectivesurface 1030 of the prism 1003I is a polygonal surface (convex surface)which is flexed to be convex in a direction pointing away from thesecond surface 1012 (i.e., away from the incident surface 1010) whenviewed from one end in the X-axis direction. In this case, thereflective surface 1030 of the prism 1003I is flexed only on a crosssection parallel to a Y-Z plane (i.e., only on a cross sectionperpendicular to the X-axis) but is linear on a cross section parallelto a X-Y plane (i.e., on a cross section perpendicular to the Z-axis).However, the example shown in FIG. 30B is only an example and should notbe construed as limiting. Alternatively, the reflective surface 1030 ofthe prism 1003I may also be a polygonal surface (concave surface) whichis flexed to be convex toward the second surface 1012 (i.e., toward theincident surface 1010) when viewed from one end in the X-axis direction.Furthermore, the reflective surface 1030 of the prism 1003I may beflexed only on a cross section parallel to the X-Y plane (i.e., only ona cross section perpendicular to the Z-axis) or may be flexed both on across section parallel to the Y-Z plane and on a cross section parallelto the X-Y plane.

Furthermore, in the example illustrated in FIG. 30C, a side surface 1031of the prism 1003J is formed as a curved surface, not as a flat surface.The side surface 1031 is a surface, intersecting with the reflectivesurface 1030 (i.e., a surface located opposite from the incident surface1010 with respect to the reflective surface 1030), out of inner surfacesof the prism 1003J. In the example illustrated in FIG. 30C, the sidesurface 1031 of the prism 1003J is a concave curved surface which isconvex in a direction pointing away from the reflective surface 1030(i.e., away from the incident surface 1010) when viewed from one end inthe X-axis direction. In this case, the side surface 1031 of the prism1003J is curved only on a cross section parallel to a Y-Z plane (i.e.,only on a cross section perpendicular to the X-axis) but is linear on across section parallel to a X-Y plane (i.e., on a cross sectionperpendicular to the Z-axis). However, the example shown in FIG. 30C isonly an example and should not be construed as limiting. Alternatively,the side surface 1031 of the prism 1003J may also be a convex curvedsurface which is curved to be convex toward the reflective surface 1030(i.e., toward the incident surface 1010) when viewed from one end in theX-axis direction. Furthermore, the side surface 1031 of the prism 1003Jmay be curved only on a cross section parallel to the X-Y plane (i.e.,only on a cross section perpendicular to the Z-axis) or may be curvedboth on a cross section parallel to the Y-Z plane and on a cross sectionparallel to the X-Y plane.

Furthermore, the side surface 1031 of the prism 1003J does not have tobe a curved surface but may also be formed as a polygonal surface aswell as the reflective surface 1030 of the prism 1003I shown in FIG.30B. In that case, as in the case of the curved surface, the sidesurface 1031 of the prism 1003J may be either a polygonal surface(concave surface) which is flexed to be convex in a direction pointingaway from the reflective surface 1030, or a polygonal surface (convexsurface) which is flexed to be convex in a direction pointing toward thereflective surface 1030, when viewed from one end in the X-axisdirection.

As can be seen from the foregoing description of this variation, a crosssection of the prism 1003 as viewed from one end in the X-axis directiondoes not have to be a triangular one but may also have any otherappropriate shape. Furthermore, the cross-sectional shapes of the prisms1003H, 1003I, 1003J described above may be adopted in combination witheach other. Alternatively, any of the cross-sectional shapes of theprisms 1003H, 1003I, 1003J may be combined with any of the shapes of theprisms 1003B, 1003C, 1003D, 1003E, 1003F, 1003G described above for thesixth variation.

Furthermore, if the reflective surface 1030 has a curved shape or apolygonal shape, then the luminous intensity distribution of the lightreflected from (the reflective surface 1030 of) the prism 1003 andemerging from the second surface 1012 (specifically, the divergenceangle or the direction of the light) may be controlled by the reflectivesurface 1030. Thus, adjusting the shape of (the reflective surface 1030of) the prism 1003 allows the luminous intensity distribution of thelight emerging from the second surface 1012 to be adapted to the opticalproperties of the display 1005 or the optical system 1320, for example.In addition, adopting an appropriate shape such as a curved or polygonalshape for at least one of the reflective surface 1030 or the sidesurface 1031 may improve the mold release ability of the light guidemember 1001 during its molding process (of its manufacturing process),thus contributing to improving the production efficiency as well.

(Other Variations)

The first surface 1011 may be a surface perpendicular to the incidentsurface 1010 while the second surface 1012 may be a surface that is notperpendicular to the incident surface 1010 but tilted with respect tothe X-Y plane. Alternatively, each of the first surface 1011 and thesecond surface 1012 may be a surface that is not perpendicular to theincident surface 1010 but is tilted to the X-Y plane.

Also, not all of the plurality of prisms 1003 have to have the sameshape. For example, the plurality of prisms 1003 may include multipledifferent types of prisms 1003, of which the reflective surfaces 1030have different tilt angles θ1, which have different longitudinaldimensions, or of which the recesses serving as the prisms 1003 havemutually different depths (i.e., which have mutually different prism1003 heights). In particular, in a display system 1300 for use as ahead-up display, to make the luminance of the virtual image displayeduniform, the intensity of the light emerging from the second surface1012 serving as an emergent surface of the light guide member 1001 issuitably uniformized. In that case, if the intensity distribution (moreexactly, the illuminance distribution) of the light on the first surface1011 is not uniform, the intensity of the light emerging from the secondsurface 1012 is suitably uniformized by changing the shape of the prisms1003 from one area of the first surface 1011 to another. In this manner,the plurality of prisms 1003 may have mutually different shapes from onearea of the first surface 1011 to another.

Also, the light guide member 1001 has only to include the direct opticalpath L10. Not all the light that has entered the light guide member 1001through the incident surface 1010 has to travel along the direct opticalpath L10. That is to say, the light guide member 1001 may include, forexample, an indirect optical path that causes the incident light to bereflected from the first surface 1011 or the second surface 1012 atleast once, be reflected from the prism 1003, and then emerge throughthe second surface 1012.

Furthermore, the first surface 1011 may be provided with only one prism1003, instead of the plurality of prisms 1003. In that case, the prism1003 may include a plurality of reflective surfaces 1030 which areformed over the entire first surface 1011 and have mutually differenttilt angles.

Also, in the second embodiment, the prism 1003 is formed by patterningthe first surface 1011 of the light guide member 1001. However, this isonly an example and should not be construed as limiting. Alternatively,the prism 1003 may be provided for the first surface 1011 by, forexample, affixing a prism sheet with the prism 1003 onto the firstsurface 1011. In that case, the prism sheet may include only a singleprism 1003 or a plurality of prisms 1003, whichever is appropriate.

Furthermore, the prism 1003 does not have to be concave with respect tothe first surface 1011 (i.e., recessed with respect to the first surface1011) but may also be convex with respect to the first surface 1011(i.e., protrude from the first surface 1011). Even such a prism 1003that is convex with respect to the first surface 1011 may have any ofvarious shapes as exemplified above for the sixth and seventhvariations.

Furthermore, the luminous intensity distribution control member 1014 hasonly to control the luminous intensity distribution of the lightextracted from the second surface 1012 and may be provided for at leastone of the first surface 1011 or the second surface 1012. Specifically,in the second embodiment, the luminous intensity distribution controlmember 1014 is provided for the second surface 1012 serving as anemergent surface. However, this configuration is only an example andshould not be construed as limiting. Alternatively, the luminousintensity distribution control member 1014 may be provided for the firstsurface 1011 or provided for both the first surface 1011 and the secondsurface 1012. Furthermore, in the second embodiment described above, theluminous intensity distribution control member 1014 is integrated withthe light guide member 1001 to form an integrally molded product.However, this is only an example and should not be construed aslimiting. Alternatively, the luminous intensity distribution controlmember 1014 may be provided for the second surface 1012 by affixing aluminous intensity distribution control sheet with the luminousintensity distribution control member 1014 to the second surface 1012,for example.

Furthermore, the luminous intensity distribution control member 1014does not have to be configured as a lens but may also be configured as adiffusive sheet, a prism, or a diffraction grating, for example.

Furthermore, the moving vehicle B1 to be equipped with the displaysystem 1300 does not have to be an automobile (passenger car) but mayalso be a large car such as a truck or a bus, a two-wheeled vehicle, arailway train, a motorized cart, a construction machine, an aircraft, ora watercraft, for example.

Furthermore, the display system 1300 does not have to be configured todisplay a virtual image as is done by a head-up display. Alternatively,the display system 1300 may also be a liquid crystal display or aprojector, for example. Still alternatively, the display system 1300 mayalso be the display of a car navigation system, an electronic mirrorsystem, or a multi-information display device, all of which may beinstalled in the moving vehicle body B11.

Furthermore, the illumination system 1200 does not have to be used inthe display system 1300 but may also be used for industrial purposes,e.g., to cure a resin or to grow plants, or for other lighting purposesincluding a guidance light.

Furthermore, the light control member 1002 is not an essentialconstituent element for the optical system 1100 but may be omitted aswell. That is to say, the optical system 1100 has only to include atleast the light guide member 1001 and the prism 1003, and the lightcontrol member 1002 may be omitted as appropriate.

Third Embodiment

An optical system 1100C according to a third embodiment includesmultiple types of prisms 1301, 1302 having mutually different shapes asshown in FIGS. 31A-31D, which is a major difference from the opticalsystem 1100 according to the second embodiment. In the followingdescription, any constituent element of this third embodiment, havingthe same function as a counterpart of the second embodiment describedabove, will be designated by the same reference numeral as thatcounterpart's, and description thereof will be omitted as appropriateherein.

Specifically, according to this embodiment, a plurality of prisms 1301,1302 are arranged side by side in the direction in which the light isincident on the incident surface 1010 (i.e., in the Y-axis direction).The plurality of prisms 1301, 1302 includes a first prism 1301 and asecond prism 1302. Between the first prism 1301 and the second prism1302, the tilt angles θ11, θ12 defined by their respective reflectivesurfaces 1030 with respect to the first surface 1011 are different fromeach other. Specifically, the reflective surface 1030 of the first prism1301 defines the tilt angle θ11 with respect to the first surface 1011,while the reflective surface 1030 of the second prism 1302 defines thetilt angle θ12 with respect to the first surface 1011. The tilt angleθ11 is larger than the tilt angle θ12. In other words, the reflectivesurface 1030 of the first prism 1301 defines a larger tilt angle withrespect to the first surface 1011 than the reflective surface 1030 ofthe second prism 1302 does.

In this embodiment, the first surface 1011 includes a first zone Z1 anda second zone Z3. The first zone Z1 is a zone in which a plurality offirst prisms 1301 are arranged. The second zone Z3 is a zone in which aplurality of second prisms 1302 are arranged. That is to say, the firstprisms 1301 and the second prisms 1302 having mutually different shapesare arranged basically separately in the first zone Z1 and the secondzone Z3, respectively. In the first zone Z1, a plurality of first prisms1301 are arranged side by side as shown in FIG. 31B. In the second zoneZ3, on the other hand, a plurality of second prisms 1302 are arrangedside by side as shown in FIG. 31D.

In addition, the first surface 1011 further includes a hybrid zone Z2between the first zone Z1 and the second zone Z3. The hybrid zone Z2 isa zone in which both the first prisms 1301 and the second prisms 1302are present. That is to say, in the hybrid zone Z2, the first prisms1301 and the second prisms 1302 are present in mixture as shown in FIG.31C.

As used herein, the phrase “present in mixture” means that the two typesof structures are present alternately. In other words, in the hybridzone Z2, a second prism 1302 may be present between a pair of firstprisms 1301 or a first prism 1301 may be present between a pair ofsecond prisms 1302. As can be seen, in the hybrid zone Z2, the firstprism 1301 and the second prism 1302 are present alternately. Providingsuch a hybrid zone Z2 prevents a zone in the vicinity of the boundarybetween the first prisms 1301 and the second prisms 1302 from beingperfectly divided into the two zones, namely, the zone in which thefirst prisms 1301 are present (i.e., the first zone Z1) and the zone inwhich the second prisms 1302 are present (i.e., the second zone Z3).

In addition, the hybrid zone Z2 is further divided into a first hybridzone Z21 and a second hybrid zone Z22. The first hybrid zone Z21 islocated closer to the first zone Z1 with respect to a halfway line C10between the first zone Z1 and the second zone Z3. The second hybrid zoneZ22 is located closer to the second zone Z3 with respect to the halfwayline C10. The first hybrid zone Z21 includes the first prisms 1301 moredensely than the second hybrid zone Z22.

Specifically, the first surface 1011 is divided in the Y-axis directioninto the first zone Z1, the hybrid zone Z2, and the second zone Z3 asshown in FIG. 31A. The first zone Z1, the hybrid zone Z2, and the secondzone Z3 are arranged in this order such that the first zone Z1 islocated closer to the light control member 1002 (i.e., to the incidentsurface 1010) than the hybrid zone Z2 or the second zone Z3 is. Inaddition, the hybrid zone Z2 is divided, at the halfway line C10 in theY-axis direction, into the first hybrid zone Z21 and the second hybridzone Z22. The first hybrid zone Z21 and the second hybrid zone Z22 arearranged in this order such that the first hybrid zone Z21 is locatedcloser to the light control member 1002 (i.e., to the incident surface1010) than the second hybrid zone Z22 is.

In addition, in the first hybrid zone Z21, the first prisms 1301 arearranged more densely than in the second hybrid zone Z22. Suppose asituation where the plurality of prisms 1301, 1302 are arranged atregular pitches, for example. In that case, in the second hybrid zoneZ22, the ratio of the second prisms 1302 to the first prisms 1301 may be2:1. In the first hybrid zone Z21, on the other hand, the ratio of thesecond prisms 1302 to the first prisms 1301 may be 1:2.

According to a variation of the third embodiment, the plurality ofprisms 1301, 1302 may further include third prisms in addition to thefirst prisms 1301 and the second prisms 1302. That is to say, theplurality of prisms 1301, 1302 may include three or more different typesof prisms 1301, 1302, of which the respective reflective surfaces 1030define mutually different tilt angles θ11, θ12 with respect to the firstsurface 1011.

Optionally, any of the various configurations that have been describedwith respect to the third embodiment (including their variations) may beadopted as appropriate in combination with any of various configurationsthat have been described with respect to the second embodiment(including their variations).

(Recapitulation)

As can be seen from the foregoing description, an optical system (100,100A-100C) according to a first aspect includes a light guide member (1)and a prism (3). The light guide member (1) has: an incident surface(10) on which light is incident; and a first surface (11) and a secondsurface (12) facing each other. The second surface (12) is a lightemergent surface. The prism (3) is provided for the first surface (11)and reflects, toward the second surface (12), the light passing insidethe light guide member (1). The light guide member (1) includes a directoptical path (L1), along which the light that has entered the lightguide member (1) through the incident surface (10) is directly reflectedfrom the prism (3) and allowed to emerge from the second surface (12).

This aspect achieves the advantage of contributing to increasing thelight extraction efficiency.

In an optical system (100, 100A-100C) according to a second aspect,which may be implemented in conjunction with the first aspect, thedirect optical path (L1) includes an optical path of light to be totallyreflected from the prism (3).

This aspect achieves the advantage of facilitating increasing the lightextraction efficiency compared to a situation where the light is nottotally reflected from the prism (3).

An optical system (100, 100A-100C) according to a third aspect, whichmay be implemented in conjunction with the first or second aspect,further includes a light control member (2) to condense light travelingtoward the incident surface (10) and direct condensed light toward theincident surface (10). The light control member (2) is integrated withthe light guide member (1).

This aspect achieves the advantage of facilitating control of the lightincident on the incident surface (10), compared to a situation where thelight control member (2) is provided separately from the light guidemember (1).

In an optical system (100, 100A) according to a fourth aspect, which maybe implemented in conjunction with any one of the first to thirdaspects, the first surface (11) and the second surface (12) are tiltedwith respect to each other.

This aspect achieves the advantage of facilitating increasing the lightextraction efficiency compared to a situation where the first surface(11) and the second surface (12) are parallel to each other.

In an optical system (100, 100A-100C) according to a fifth aspect, whichmay be implemented in conjunction with any one of the first to fourthaspects, the light guide member (1) further includes an indirect opticalpath (L2), along which the light that has entered the light guide member(1) through the incident surface (10) is once reflected from the secondsurface (12), reflected again from the prism (3), and then allowed toemerge from the second surface (12).

This aspect achieves the advantage of facilitating control of thedirection of the light emerging from the second surface (12).

In an optical system (100, 100A-100C) according to a sixth aspect, whichmay be implemented in conjunction with any one of the first to fifthaspects, the prism (3) includes a plurality of prisms (3) arranged sideby side in a direction in which the light is incident on the incidentsurface (10).

This aspect achieves the advantage of contributing to increasing thelight extraction efficiency.

In an optical system (100A) according to a seventh aspect, which may beimplemented in conjunction with any one of the first to sixth aspects,the prism (3) is tilted at least partially with respect to the incidentsurface (10) when viewed in a direction in which the first surface (11)and the second surface (12) are arranged.

This aspect achieves the advantage of facilitating control of thedirection of the light emerging from the second surface (12).

In an optical system (100, 100A-100C) according to an eighth aspect,which may be implemented in conjunction with any one of the first toseventh aspects, the prism (3) includes a plurality of small prisms (31)divided to be spaced apart from each other.

This aspect achieves the advantage of allowing the prism (3) to beformed more easily on the first surface (11), compared to a situationwhere the prism (3) is not divided.

In an optical system (100A) according to a ninth aspect, which may beimplemented in conjunction with the eighth aspect, two or more of theplurality of small prisms (31) are arranged side by side to draw a curvewhen viewed in a direction in which the first surface (11) and thesecond surface (12) are arranged.

This aspect achieves the advantage of facilitating control of thedirection of the light emerging from the second surface (12).

In an optical system (1100, 1100A-1100C) according to a tenth aspect,which may be implemented in conjunction with any one of the first toninth aspects, an optical axis (Ax1) of the light incident through theincident surface (1010) is tilted with respect to the first surface(1011) such that a gap distance between the optical axis (Ax1) and thefirst surface (1011) narrows as a distance from the incident surface(1010) increases.

According to this aspect, the light incident through the incidentsurface (1010) comes closer toward the first surface (1011) as thedistance from the incident surface (1010) increases (i.e., as the lighttravels deeper inside the light guide member (1001)). This increases thechances of the incoming light being incident on the prism (1003,1003A-1003J). In other words, this reduces the chances of most of theincoming light incident through the incident surface (1010) reaching theother end face, located opposite from the incident surface (1010), ofthe light guide member (1001), thus reducing leakage of the light fromthe end face. Consequently, this facilitates increasing the proportionof the light, traveling along the direct optical path (L10) to emergefrom the second surface (1012, 1012A) out of the light guide member(1001), to the light that has been incident through the incident surface(1010), thus contributing to increasing the light extraction efficiency.

An optical system (1100, 1100A-1100C) according to an eleventh aspect,which may be implemented in conjunction with the tenth aspect, furtherincludes a light control member (1002, 1002B, 1002C). The light controlmember (1002, 1002B, 1002C) is located between a light source (1004) andthe incident surface (1010) and controls light that has been emittedfrom the light source (1004) and is going to be incident on the incidentsurface (1010).

This aspect may contribute to further increasing the light extractionefficiency by making the light control member (1002, 1002B, 1002C)control the light incident on the incident surface (1010).

In an optical system (1100, 1100A-100C) according to a twelfth aspect,which may be implemented in conjunction with the eleventh aspect, thelight control member (1002, 1002B, 1002C) has the function ofsubstantially collimating the light emitted from the light source (1004)into parallel rays.

This aspect may substantially collimate the light incident on theincident surface (1010) into parallel rays, thus contributing to furtherincreasing the light extraction efficiency.

In an optical system (1100, 1100A-1100C) according to a thirteenthaspect, which may be implemented in conjunction with the eleventh ortwelfth aspect, the light control member (1002, 1002B, 1002C) isintegrated with the light guide member (1001). The light control member(1002, 1002B, 1002C) includes a path generating portion (1023). The pathgenerating portion (1023) extends along a line tilted with respect tothe first surface (1011) when viewed from the incident surface (1010)and forms a path for the light between the light source (1004) and theincident surface (1010).

According to this aspect, the light emitted from the light source (1004)is incident on the incident surface (1010) after having passed insidethe path generating portion (1023), thus allowing cutting down the lossof the light emitted from the light source (1004) before the lightreaches the incident surface (1010).

In an optical system (1100, 1100A-1100C) according to a fourteenthaspect, which may be implemented in conjunction with any one of thefirst to thirteenth aspects, at least one of the first surface (1011) orthe second surface (1012, 1012A) includes a luminous intensitydistribution control member (1014, 1014A, 1014B) to control a luminousintensity distribution of light to be extracted from the second surface(1012, 1012A).

According to this aspect, the luminous intensity distribution of thelight to be extracted from the second surface (1012, 1012A) of the lightguide member (1001) may be controlled by the luminous intensitydistribution control member (1014, 1014A, 1014B) provided for the lightguide member (1001). In particular, the light, passing through thedirect optical path (L10) after having entered the light guide member(1001) through the incident surface (1010), is reflected only once fromthe prism (1003, 1003A-1003J), without being reflected by any membersother than the prism (1003, 1003A-1003J), before emerging from thesecond surface (1012, 1012A) out of the light guide member (1001). Thus,the shapes of the first surface (1011) and the second surface (1012,1012A) do not contribute to guiding the light inside the light guidemember (1001). Therefore, even if the luminous intensity distributioncontrol member (1014, 1014A, 1014B) is provided for the light guidemember (1001), the light guiding performance of the light guide member(1001) hardly deteriorates. Consequently, this allows the lighttraveling along the direct optical path (L10) to be extractedefficiently from the second surface (1012, 1012A) out of the light guidemember (1001) while enabling the luminous intensity distribution to becontrolled, thus contributing to increasing the light extractionefficiency.

In an optical system (1100, 1100A-1100C) according to a fifteenthaspect, which may be implemented in conjunction with the fourteenthaspect, the luminous intensity distribution control member (1014, 1014A,1014B) is provided for the second surface (1012, 1012A).

According to this aspect, the light transmitted through the secondsurface (1012, 1012A) may have its luminous intensity distributionefficiently controlled by the luminous intensity distribution controlmember (1014, 1014A, 1014B).

In an optical system (1100, 1100A-1100C) according to a sixteenthaspect, which may be implemented in conjunction with the fourteenth orfifteenth aspect, the luminous intensity distribution control member(1014, 1014A, 1014B) includes a lens.

This aspect may eliminate the need to separately provide a lens sheet orother suitable optical members by imparting a lens function to theluminous intensity distribution control member (1014, 1014A, 1014B),thus cutting down the number of parts required.

In an optical system (1100, 1100A-1100C) according to a seventeenthaspect, which may be implemented in conjunction with the sixteenthaspect, the luminous intensity distribution control member (1014, 1014A,1014B) includes a multi-lens configured as a group of multiple smalllenses (1141).

This aspect may eliminate the need to separately provide a multi-lenssheet or other suitable optical members by imparting a multi-lensfunction to the luminous intensity distribution control member (1014,1014A, 1014B), thus cutting down the number of parts required.

In an optical system (1100, 1100A-1100C) according to an eighteenthaspect, which may be implemented in conjunction with the sixteenthaspect, the luminous intensity distribution control member (1014, 1014A,1014B) includes a Fresnel lens.

This aspect may contribute to reducing the thickness of the luminousintensity distribution control member (1014, 1014A, 1014B).

An optical system (1100, 1100A-1100C) according to a nineteenth aspect,which may be implemented in conjunction with any one of the first toeighteenth aspects, further includes a light control member (1002,1002B, 1002C). The light control member (1002, 1002B, 1002C) is locatedbetween a light source (1004) and the incident surface (1010). The lightcontrol member (1002, 1002B, 1002C) controls light that has been emittedfrom the light source (1004) and is going to be incident on the incidentsurface (1010). The light control member (1002, 1002B, 1002C) has ashape transformation function of transforming a shape projected onto aprojection plane (S1), provided parallel to the incident surface (1010),from a first shape (F1) of the light emitted from the light source(1004) into a second shape (F2) of the light that is going to beincident on the incident surface (1010).

This aspect allows the range that the light incident through theincident surface (1010) may reach inside the light guide member (1001)to be controlled irrespective of the first shape (F1) that is the shapeof the light emitted from the light source (1004). That is to say, therange that the light incident through the incident surface (1010) mayreach inside the light guide member (1001) derives from the second shape(F2) that is the shape of the light that is going to be incident on theincident surface (1010). In addition, this optical system (1100,1100A-1100C) may transform the shape from the first shape (F1) into thesecond shape (F2). Thus, this optical system (1100, 1100A-1100C) maycontrol the light incident through the incident surface (1010) so thatthe light may reach a relatively broad range inside the light guidemember (1001). Consequently, this optical system (1100, 1100A-1100C)increases the chances of the light reaching the entire first surface(1011), thus facilitating uniformly extracting the light from the entiresecond surface (1012, 1012A) serving as the emergent surface.

In an optical system (1100, 1100A-1100C) according to a twentiethaspect, which may be implemented in conjunction with the nineteenthaspect, a circumcircle of the second shape (F2) is larger than acircumcircle of the first shape (F1).

According to this aspect, the second shape (F2) comes to have anexpanded shape, compared to the first shape (F1), thus facilitatingincreasing the light extraction efficiency.

In an optical system (1100, 1100A-1100C) according to a twenty-firstaspect, which may be implemented in conjunction with the nineteenth ortwentieth aspect, the second shape (F2) is formed by adding at least onecorner portion (F21) to the first shape (F1) such that the first shape(F1) is made closer to a polygonal shape.

According to this aspect, the second shape (F2) comes to have anexpanded shape, compared to the first shape (F1), thus facilitatingincreasing the light extraction efficiency.

In an optical system (1100, 1100A-1100C) according to a twenty-secondaspect, which may be implemented in conjunction with any one of thenineteenth to twenty-first aspects, the light control member (1002,1002B, 1002C) has a plurality of lens surfaces (1201-1205) on a countersurface thereof facing the light source (1004).

This aspect allows the light emitted from the light source (1004) toenter the light control member (1002, 1002B, 1002C) more easily.

An optical system (1100, 1100A-1100C) according to a twenty-thirdaspect, which may be implemented in conjunction with any one of thefirst to twenty-second aspects, further includes a light control member(1002) located between a light source (1004) and the incident surface(1010) and configured to control light that has been emitted from thelight source (1004) and is going to be incident on the incident surface(1010). The light control member (1002) includes an incident lens (1021)and an outlet portion (1022). The light control member (1002) allows thelight that has been incident on the incident lens (1021) from the lightsource (1004) to go out of the light control member from the outletportion (1022). The incident lens (1021) has a main incident surface(1211) and an auxiliary incident surface (1212). The main incidentsurface (1211) is arranged to face the light source (1004). Theauxiliary incident surface (1212) is arranged to face toward a normal(L21) to the main incident surface (1211) and located at least partiallyalong a circumference of the main incident surface (1211). An opticalaxis (Ax2) of the light source (1004) is tilted with respect to thenormal (L21) to the main incident surface (1211).

According to this aspect, the light emitted from the light source (1004)is incident on the incident lens (1021) of the optical member (1020)asymmetrically to the normal (L21) to the main incident surface (1211).This allows making the intensity of the light incident from the lightsource (1004) imbalanced between the main incident surface (1211) of theincident lens (1021) and the auxiliary incident surface (1212) locatedaround the main incident surface (1211). Consequently, this allows theoptical member (1020) to have increased light harvesting efficiency.

In an optical system (1100, 1100A-1100C) according to a twenty-fourthaspect, which may be implemented in conjunction with the twenty-thirdaspect, light rays that have been incident on the incident lens (1021)from the light source (1004) include a principal ray (L11) and a firstauxiliary ray (L12) and a second auxiliary ray (L13), both of which havea lower intensity than the principal ray (L11). The principal ray (L11),the first auxiliary ray (L12), and the second auxiliary ray (L13) arearranged in this order in a direction perpendicular to a normal (L21) tothe main incident surface (1211).

According to this aspect, the principal ray (L11), the first auxiliaryray (L12), and the second auxiliary ray (L13) are arranged in thedescending order of their intensity, thus enabling the principal ray(L11) with a relatively high intensity to be extracted more easily.

In an optical system (1100, 1100A-1100C) according to a twenty-fifthaspect, which may be implemented in conjunction with the twenty-fourthaspect, the intensity of the principal ray (L11) is a maximum intensityamong the light rays that have been incident on the incident lens (1021)from the light source (1004).

This aspect enables the principal ray (L11) with the maximum intensityto be extracted more easily.

An illumination system (200, 1200) according to a twenty-sixth aspectincludes the optical system (100, 100A-100C, 1100, 1100A-1100C)according to any one of the first to twenty-fifth aspects and a lightsource (4, 1004). The light source (1004) emits light toward theincident surface (10, 1010) through the light control member (2, 1002).

This aspect achieves the advantage of contributing to increasing thelight extraction efficiency.

A display system (300, 1300) according to a twenty-seventh aspectincludes the illumination system (200, 1200) according to thetwenty-sixth aspect and a display (5, 1005). The display (5, 1005)receives the light emerging from the illumination system (200, 1200) anddisplays an image thereon.

This aspect achieves the advantage of contributing to increasing thelight extraction efficiency.

A moving vehicle (B1) according to a twenty-eighth aspect includes thedisplay system (300, 1300) according to the twenty-seventh aspect and amoving vehicle body (B11) to be equipped with the display system (300,1300).

This aspect achieves the advantage of contributing to increasing thelight extraction efficiency.

Note that the constituent elements according to the second totwenty-fifth aspects are not essential constituent elements for theoptical system (100, 100A-100C, 1100, 1100A-1100C) but may be omitted asappropriate.

The present disclosure has the following twenty-ninth to fortiethaspects. The twenty-ninth to fortieth aspects of the present disclosuregenerally relate to an optical system, an illumination system, a displaysystem, and a moving vehicle. More specifically, the twenty-ninth tofortieth aspects of the present disclosure relate to an optical systemconfigured to control light which has been incident through an incidentsurface to make the light emerge from an emergent surface, anillumination system, a display system, and a moving vehicle. An objectof the twenty-ninth to fortieth aspects of the present disclosure is toprovide an optical system, an illumination system, a display system, anda moving vehicle, all of which are configured to contribute toincreasing the light extraction efficiency.

An optical system (100, 100A-100C) according to a twenty-ninth aspectincludes a light guide plate (light guide member 1), a light controlmember (2), and a prism (3). The light guide plate (light guide member1) has an incident surface (10) on which light is incident; and a firstsurface (11) and a second surface (12) facing each other. The secondsurface (12) is a light emergent surface. The light control member (2)condenses light traveling toward the incident surface (10) and directscondensed light toward the incident surface (10). The prism (3) isprovided for the first surface (11) and reflects, toward the secondsurface (12), the light passing inside the light guide plate (lightguide member 1). The light guide plate (light guide member 1) includes adirect optical path (L1), along which the light that has entered thelight guide member (1) through the incident surface (10) is directlyreflected from the prism (3) and allowed to emerge from the secondsurface (12).

This aspect achieves the advantage of contributing to increasing thelight extraction efficiency.

In an optical system (100, 100A-100C) according to a thirtieth aspect,which may be implemented in conjunction with the twenty-ninth aspect,the direct optical path (L1) includes an optical path of light to betotally reflected from the prism (3).

This aspect achieves the advantage of facilitating increasing the lightextraction efficiency compared to a situation where the light is nottotally reflected from the prism (3).

In an optical system (100, 100A-100C) according to a thirty-firstaspect, which may be implemented in conjunction with the twenty-ninth orthe thirtieth aspect, the light control member (2) is integrated withthe light guide plate (light guide member 1).

This aspect achieves the advantage of facilitating control of the lightincident on the incident surface (10), compared to a situation where thelight control member (2) is provided separately from the light guideplate (light guide member 1).

In an optical system (100, 100A) according to a thirty-second aspect,which may be implemented in conjunction with any one of the twenty-ninthto thirty-first aspects, the first surface (11) and the second surface(12) are tilted with respect to each other.

This aspect achieves the advantage of facilitating increasing the lightextraction efficiency compared to a situation where the first surface(11) and the second surface (12) are parallel to each other.

In an optical system (100, 100A-100C) according to a thirty-thirdaspect, which may be implemented in conjunction with any one of thetwenty-ninth to thirty-second aspects, the light guide plate (lightguide member 1) further includes an indirect optical path (L2), alongwhich the light that has entered the light guide member (1) through theincident surface (10) is once reflected from the second surface (12),reflected again from the prism (3), and then allowed to emerge from thesecond surface (12).

This aspect achieves the advantage of facilitating control of thedirection of the light emerging from the second surface (12).

In an optical system (100, 100A-100C) according to a thirty-fourthaspect, which may be implemented in conjunction with any one of thetwenty-ninth to thirty-third aspects, the prism (3) includes a pluralityof prisms (3) arranged side by side in a direction in which the light isincident on the incident surface (10).

This aspect achieves the advantage of contributing to increasing thelight extraction efficiency.

In an optical system (100A) according to a thirty-fifth aspect, whichmay be implemented in conjunction with any one of the twenty-ninth tothirty-fourth aspects, the prism (3) is tilted at least partially withrespect to the incident surface (10) when viewed in a direction in whichthe first surface (11) and the second surface (12) are arranged.

This aspect achieves the advantage of facilitating control of thedirection of the light emerging from the second surface (12).

In an optical system (100, 100A-100C) according to a thirty-sixthaspect, which may be implemented in conjunction with any one of thetwenty-ninth to thirty-fifth aspects, the prism (3) includes a pluralityof small prisms (31) divided to be spaced apart from each other.

This aspect achieves the advantage of allowing the prism (3) to beformed more easily on the first surface (11), compared to a situationwhere the prism (3) is not divided.

In an optical system (100A) according to a thirty-seventh aspect, whichmay be implemented in conjunction with the thirty-sixth aspect, two ormore of the plurality of small prisms (31) are arranged side by side todraw a curve when viewed in a direction in which the first surface (11)and the second surface (12) are arranged.

This aspect achieves the advantage of facilitating control of thedirection of the light emerging from the second surface (12).

An illumination system (200) according to a thirty-eighth aspectincludes the optical system (100, 100A-100C) according to any one of thetwenty-ninth to thirty-seventh aspects and a light source (4). The lightsource (4) emits light toward the incident surface (10) through thelight control member (2).

This aspect achieves the advantage of contributing to increasing thelight extraction efficiency.

A display system (300) according to a thirty-ninth aspect includes theillumination system (200) according to the thirty-eighth aspect and adisplay (5). The display (5) receives the light emerging from theillumination system (200) and displays an image thereon.

This aspect achieves the advantage of contributing to increasing thelight extraction efficiency.

A moving vehicle (B1) according to a fortieth aspect includes thedisplay system (300) according to the thirty-ninth aspect and a movingvehicle body (B11) to be equipped with the display system (300).

This aspect achieves the advantage of contributing to increasing thelight extraction efficiency.

Note that the constituent elements according to the thirtieth tothirty-seventh aspects are not essential constituent elements for theoptical system (100) but may be omitted as appropriate.

The present disclosure has the following forty-first to forty-ninthaspects. The forty-first to forty-ninth aspects of the presentdisclosure generally relate to an optical system, an illuminationsystem, a display system, and a moving vehicle. More specifically, theforty-first to forty-ninth aspects of the present disclosure relate toan optical system configured to control light which has been incidentthrough an incident surface to make the light emerge from an emergentsurface, an illumination system, a display system, and a moving vehicle.An object of the forty-first to forty-ninth aspects of the presentdisclosure is to provide an optical system, an illumination system, adisplay system, and a moving vehicle, all of which are configured tocontribute to increasing the light extraction efficiency.

An optical system (1100, 1100A-1100C) according to a forty-first aspectincludes a light guide member (1001) and a prism (1003, 1003A-1003J).The light guide member (1001) has: an incident surface (1010) on whichlight is incident; and a first surface (1011) and a second surface(1012, 1012A) facing each other. The second surface (1012, 1012A) of thelight guide member (1001) is a light emergent surface. The prism (1003,1003A-1003J) is provided for the first surface (1011) and reflects,toward the second surface (1012, 1012A), the light passing inside thelight guide member (1001). The light guide member (1001) includes adirect optical path (L10), along which the light that has entered thelight guide member (1001) through the incident surface (1010) isdirectly reflected from the prism (1003, 1003A-1003J) and allowed toemerge from the second surface (1012, 1012A). An optical axis (Ax1) ofthe light incident through the incident surface (1010) is tilted withrespect to the first surface (1011) such that a gap distance between theoptical axis (Ax1) and the first surface (1011) narrows as a distancefrom the incident surface (1010) increases.

According to this aspect, the light incident through the incidentsurface (1010) comes closer toward the first surface (1011) as thedistance from the incident surface (1010) increases (i.e., as the lighttravels deeper inside the light guide member (1001)). This increases thechances of the incoming light being incident on the prism (1003,1003A-1003J). In other words, this reduces the chances of most of theincoming light incident through the incident surface (1010) reaching theother end face, located opposite from the incident surface (1010), ofthe light guide member (1001), thus reducing leakage of the light fromthe end face. Consequently, this facilitates increasing the proportionof the light, traveling along the direct optical path (L10) to emergefrom the second surface (1012, 1012A) out of the light guide member(1001), to the light that has been incident through the incident surface(1010), thus contributing to increasing the light extraction efficiency.

An optical system (1100, 1100A-1100C) according to a forty-secondaspect, which may be implemented in conjunction with the forty-firstaspect, further includes a light control member (1002, 1002B, 1002C).The light control member (1002, 1002B, 1002C) is located between a lightsource (1004) and the incident surface (1010) and controls light thathas been emitted from the light source (1004) and is going to beincident on the incident surface (1010).

This aspect may contribute to further increasing the light extractionefficiency by making the light control member (1002, 1002B, 1002C)control the light that is going to be incident on the incident surface(1010).

In an optical system (1100, 1100A-100C) according to a forty-thirdaspect, which may be implemented in conjunction with the forty-secondaspect, the light control member (1002, 1002B, 1002C) has the functionof substantially collimating the light emitted from the light source(1004) into parallel rays.

This aspect may substantially collimate the light incident on theincident surface (1010) into parallel rays, thus contributing to furtherincreasing the light extraction efficiency.

In an optical system (1100, 1100A-1100C) according to a forty-fourthaspect, which may be implemented in conjunction with the forty-second orforty-third aspects, the light control member (1002, 1002B, 1002C) isintegrated with the light guide member (1001). The light control member(1002, 1002B, 1002C) includes a path generating portion (1023). The pathgenerating portion (1023) extends along a line tilted with respect tothe first surface (1011) when viewed from the incident surface (1010)and forms a path for the light between the light source (1004) and theincident surface (1010).

According to this aspect, the light emitted from the light source (1004)is incident on the incident surface (1010) after having passed insidethe path generating portion (1023), thus allowing cutting down the lossof the light emitted from the light source (1004) before the lightreaches the incident surface (1010).

In an optical system (1100, 1100A-1100C) according to a forty-fifthaspect, which may be implemented in conjunction with the forty-first orforty-fourth aspect, light rays reaching the second surface (1012,1012A) after having traveled along the direct optical path (L10) are allincident on the second surface (1012, 1012A) at the same angle ofincidence.

This aspect allows the directions of the light rays emerging from thesecond surface (1012, 1012A) to be aligned with each other.

In an optical system (1100, 1100A-1100C) according to a forty-sixthaspect, which may be implemented in conjunction with any one of theforty-first or forty-fifth aspect, the light emerging from the secondsurface (1012, 1012A) after having traveled along the direct opticalpath (L10) accounts for 50% or more of the light that has entered thelight guide member (1001) through the incident surface (1010).

This aspect allows the light extraction efficiency to be increasedsignificantly.

An illumination system (1200) according to a forty-seventh aspectincludes the optical system (1100, 1100A-1100C) according to any one ofthe forty-first to forty-sixth aspects and a light source (1004). Thelight source (1004) emits light toward the incident surface (1010).

This aspect achieves the advantage of contributing to increasing thelight extraction efficiency.

A display system (1300) according to a forty-eighth aspect includes theillumination system (1200) according to the forty-seventh aspect and adisplay (1005). The display (1005) receives the light emerging from theillumination system (1200) and displays an image thereon.

This aspect achieves the advantage of contributing to increasing thelight extraction efficiency.

A moving vehicle (B1) according to a forty-ninth aspect includes thedisplay system (1300) according to the forty-eighth aspect and a movingvehicle body (B11) to be equipped with the display system (1300).

This aspect achieves the advantage of contributing to increasing thelight extraction efficiency.

Note that the constituent elements according to the forty-second toforty-sixth aspects are not essential constituent elements for theoptical system (1100, 1100A-1100C) but may be omitted as appropriate.

The present disclosure has the following fiftieth to fifty-ninthaspects. The fiftieth to fifty-ninth aspects of the present disclosuregenerally relate to an optical system, an illumination system, a displaysystem, and a moving vehicle. More specifically, the fiftieth tofifty-ninth aspects of the present disclosure relate to an opticalsystem configured to control light which has been incident through anincident surface to make the light emerge from an emergent surface, anillumination system, a display system, and a moving vehicle. An objectof the fiftieth to fifty-ninth aspects of the present disclosure is toprovide an optical system, an illumination system, a display system, anda moving vehicle, all of which are configured to facilitate extractinglight uniformly from the entire emergent surface.

An optical system (1100, 1100A-1100C) according to a fiftieth aspectincludes a light guide member (1001), a prism (1003, 1003A-1003J), and alight control member (1002, 1002B, 1002C). The light guide member (1001)has an incident surface (1010) on which light is incident; and a firstsurface (1011) and a second surface (1012, 1012A) facing each other. Thesecond surface (1012, 1012A) of the light guide member (1001) is a lightemergent surface. The prism (1003, 1003A-1003J) is provided for thefirst surface (1011) and reflects, toward the second surface (1012,1012A), the light passing inside the light guide member (1001). Thelight control member (1002, 1002B, 1002C) is located between a lightsource (1004) and the incident surface (1010). The light control member(1002, 1002B, 1002C) controls light that has been emitted from the lightsource (1004) and is going to be incident on the incident surface(1010). The light guide member (1001) includes a direct optical path(L10), along which the light that has entered the light guide member(1001) through the incident surface (1010) is directly reflected fromthe prism (1003, 1003A-1003J) and allowed to emerge from the secondsurface (1012, 1012A). The light control member (1002, 1002B, 1002C) hasa shape transformation function of transforming a shape projected onto aprojection plane (S1), provided parallel to the incident surface (1010),from a first shape (F1) of the light emitted from the light source(1004) into a second shape (F2) of the light that is going to beincident on the incident surface (1010).

This aspect allows the range that the light incident through theincident surface (1010) may reach inside the light guide member (1001)to be controlled irrespective of the first shape (F1) that is the shapeof the light emitted from the light source (1004). That is to say, therange that the light incident through the incident surface (1010) mayreach inside the light guide member (1001) derives from the second shape(F2) that is the shape of the light incident on the incident surface(1010). In addition, this optical system (1100, 1100A-1100C) maytransform the shape from the first shape (F1) into the second shape(F2). Thus, this optical system (1100, 1100A-1100C) may control thelight incident through the incident surface (1010) so that the light mayreach a relatively broad range inside the light guide member (1001).Consequently, this optical system (1100, 1100A-1100C) increases thechances of the light reaching the entire first surface (1011), thusfacilitating uniformly extracting the light from the entire secondsurface (1012, 1012A) serving as the emergent surface.

In an optical system (1100, 1100A-1100C) according to a fifty-firstaspect, which may be implemented in conjunction with the fiftiethaspect, a circumcircle of the second shape (F2) is larger than acircumcircle of the first shape (F1).

According to this aspect, the second shape (F2) comes to have anexpanded shape, compared to the first shape (F1), thus facilitatingincreasing the light extraction efficiency.

In an optical system (1100, 1100A-1100C) according to a fifty-secondaspect, which may be implemented in conjunction with the fiftieth orfifty-first aspect, the second shape (F2) is formed by adding at leastone corner portion (F21) to the first shape (F1) such that the firstshape (F1) is made closer to a polygonal shape.

According to this aspect, the second shape (F2) comes to have anexpanded shape, compared to the first shape (F1), thus facilitatingincreasing the light extraction efficiency.

An optical system (1100, 1100A-1100C) according to a fifty-third aspect,which may be implemented in conjunction with any one of the fiftieth tofifty-second aspects, includes a plurality of light sources (1004), oneof which is the light source (1004), and a plurality of light controlmembers (1002, 1002B, 1002C), one of which is the light control member(1002, 1002B, 1002C).

This aspect allows the light that has come from the plurality of lightsources (1004) and the plurality of light control members (1002, 1002B,1002C) to enter the light guide member (1001) more easily.

In an optical system (1100, 1100A-1100C) according to a fifty-fourthaspect, which may be implemented in conjunction with any one of thefiftieth to fifty-third aspects, the light control member (1002, 1002B,1002C) has, on its surface facing the light source (1004), a pluralityof lens surfaces (1201-1205).

This aspect allows the light emitted from the light source (1004) toenter the light control member (1002, 1002B, 1002C) more easily.

In an optical system (1100, 1100A-1100C) according to a fifty-fifthaspect, which may be implemented in conjunction with any one of thefiftieth to fifty-fourth aspects, a tilt angle defined by a countersurface, facing the light source (1004), of the light control member(1002, 1002B, 1002C) with respect to a counter axis facing the lightsource (1004) varies along a circumference around the counter axis.

This aspect allows the light emitted from the light source (1004) toenter the light control member (1002, 1002B, 1002C) more easily.

In an optical system (1100, 1100A-1100C) according to a fifty-sixthaspect, which may be implemented in conjunction with any one of thefiftieth to fifty-fifth aspects, a counter surface, facing the lightsource (1004), of the light control member (1002, 1002B, 1002C) has anasymmetric shape in one direction perpendicular to the counter axisfacing the light source (1004).

This aspect facilitates reducing the thickness of the light controlmember (1002, 1002B, 1002C).

An illumination system (1200) according to a fifty-seventh aspectincludes the optical system (1100, 1100A-1100C) according to any one ofthe fiftieth to fifty-sixth aspects and a light source (1004). The lightsource (1004) emits light to be incident on the incident surface (1010).

This aspect facilitates extracting light uniformly from the entireemergent surface.

A display system (1300) according to a fifty-eighth aspect includes theillumination system (1200) according to the fifty-seventh aspect and adisplay (1005). The display (1005) receives the light emerging from theillumination system (1200) and displays an image thereon.

This aspect facilitates extracting light uniformly from the entireemergent surface.

A moving vehicle (B1) according to a fifty-ninth aspect includes thedisplay system (1300) according to the fifty-eighth aspect and a movingvehicle body (B11) to be equipped with the display system (1300).

This aspect facilitates extracting light uniformly from the entireemergent surface.

Note that the constituent elements according to the fifty-first tofifty-sixth aspects are not essential constituent elements for theoptical system (1100, 1100A-1100C) but may be omitted as appropriate.

The present disclosure has the following sixtieth to sixty-ninthaspects. The sixtieth to sixty-ninth aspects of the present disclosuregenerally relate to an optical member, an optical system, anillumination system, a display system, and a moving vehicle. Morespecifically, the sixtieth to sixty-ninth aspects of the presentdisclosure relate to an optical member including an incident lens, anoptical system, an illumination system, a display system, and a movingvehicle. An object of the sixtieth to sixty-ninth aspects of the presentdisclosure is to provide an optical member, an optical system, anillumination system, a display system, and a moving vehicle, all ofwhich are configured to contribute to increasing the light harvestingefficiency.

An optical member (1020) according to a sixtieth aspect includes anincident lens (1021) and an outlet portion (1022). The optical member(1020) allows the light that has been incident on the incident lens(1021) from the light source (1004) to go out of the optical member(1020) from the outlet portion (1022). The incident lens (1021) has amain incident surface (1211) and an auxiliary incident surface (1212).The main incident surface (1211) is arranged to face the light source(1004). The auxiliary incident surface (1212) is arranged to face towarda normal (L21) to the main incident surface (1211) and located at leastpartially along a circumference of the main incident surface (1211). Anoptical axis (Ax2) of the light source (1004) is tilted with respect tothe normal (L21) to the main incident surface (1211).

According to this aspect, the light emitted from the light source (1004)is incident on the incident lens (1021) of the optical member (1020)asymmetrically to the normal (L21) to the main incident surface (1211).This allows making the intensity of the light incident from the lightsource (1004) imbalanced between the main incident surface (1211) of theincident lens (1021) and the auxiliary incident surface (1212) locatedaround the main incident surface (1211). Consequently, this allows theoptical member (1020) to have increased light harvesting efficiency.

In an optical member (1020) according to a sixty-first aspect, which maybe implemented in conjunction with the sixtieth aspect, light rays thathave been incident on the incident lens (1021) from the light source(1004) include a principal ray (L11) and a first auxiliary ray (L12) anda second auxiliary ray (L13), both of which have a lower intensity thanthe principal ray (L11). The principal ray (L11), the first auxiliaryray (L12), and the second auxiliary ray (L13) are arranged in this orderin a direction perpendicular to a normal (L21) to the main incidentsurface (1211).

According to this aspect, the principal ray (L11), the first auxiliaryray (L12), and the second auxiliary ray (L13) are arranged in thedescending order of their intensity, thus enabling the principal ray(L11) with a relatively high intensity to be extracted more easily.

In an optical member (1020) according to a sixty-second aspect, whichmay be implemented in conjunction with the sixty-first aspect, anintensity of the principal ray (L11) is a maximum intensity among thelight rays that have been incident on the incident lens (1021) from thelight source (1004).

This aspect enables the principal ray (L11) with the maximum intensityto be extracted more easily.

In an optical member (1020) according to a sixty-third aspect, which maybe implemented in conjunction with the sixty-first or sixty-secondaspect, the principal ray (L11) is incident on the auxiliary incidentsurface (1212).

This aspect allows the principal ray (L11) to be extracted efficiently.

In an optical member (1020) according to a sixty-fourth aspect, whichmay be implemented in conjunction with any one of the sixtieth tosixty-third aspects, the auxiliary incident surface (1212) has anasymmetric shape with respect to a normal (L21) to the main incidentsurface (1211).

This aspect allows reducing the thickness of the optical member (1020)more easily than in a situation where the auxiliary incident surface(1212) has a symmetric shape.

An optical system (1100, 1100A-1100C) according to a sixty-fifth aspectincludes the optical member (1020) according to any one of the sixtiethto sixty-fourth aspects, a light guide member (1001), and a prism (1003,1003A-1003J). The light guide member (1001) has an incident surface(1010) on which light is incident; and a first surface (1011) and asecond surface (1012, 1012A) facing each other. The second surface(1012, 1012A) of the light guide member (1001) is a light emergentsurface. The prism (1003, 1003A-1003J) is provided for the first surface(1011) and reflects, toward the second surface (1012, 1012A), the lightpassing inside the light guide member (1001). The optical member (1020)is located between a light source (1004) and the incident surface (1010)and controls light that has been emitted from the light source (1004)and is going to be incident on the incident surface (1010).

This aspect may contribute to increasing the light harvestingefficiency.

In an optical system (1100, 1100A-1100C) according to a sixty-sixthaspect, which may be implemented in conjunction with the sixty-fifthaspect, the light guide member (1001) includes a direct optical path(L10), along which the light that has entered the light guide member(1001) through the incident surface (1010) is directly reflected fromthe prism (1003, 1003A-1003J) and allowed to emerge from the secondsurface (1012, 1012A).

This aspect may contribute to increasing the light harvestingefficiency.

An illumination system (1200) according to a sixty-seventh aspectincludes the optical system (1100, 1100A-1100C) according to thesixty-fifth or sixty-sixth aspect and a light source (1004). The lightsource (1004) emits light to be incident on the incident surface (1010).

This aspect achieves the advantage of contributing to increasing thelight harvesting efficiency.

A display system (1300) according to a sixty-eighth aspect includes theillumination system (1200) according to the sixty-seventh aspect and adisplay (1005). The display (1005) receives the light emerging from theillumination system (1200) and displays an image thereon.

This aspect achieves the advantage of contributing to increasing thelight harvesting efficiency.

A moving vehicle (B1) according to a sixty-ninth aspect includes thedisplay system (1300) according to the sixty-eighth aspect and a movingvehicle body (B11) to be equipped with the display system (1300).

This aspect achieves the advantage of contributing to increasing thelight harvesting efficiency.

Note that the constituent elements according to the sixty-first tosixty-fourth aspects are not essential constituent elements for theoptical member (1020) but may be omitted as appropriate.

Also, the constituent elements according to the sixty-sixth aspect arenot essential constituent elements for the optical system (1100,1100A-1100C) but may be omitted as appropriate.

The present disclosure has the following seventieth to eighty-fourthaspects. The seventieth to eighty-fourth aspects of the presentdisclosure generally relate to an optical system, an illuminationsystem, a display system, and a moving vehicle. More specifically, theseventieth to eighty-fourth aspects of the present disclosure relate toan optical system configured to control light which has been incidentthrough an incident surface to make the light emerge from an emergentsurface, an illumination system, a display system, and a moving vehicle.An object of the seventieth to eighty-fourth aspects of the presentdisclosure is to provide an optical system, an illumination system, adisplay system, and a moving vehicle, all of which are configured tocontribute to increasing the light extraction efficiency.

An optical system (1100, 1100A-1100C) according to a seventieth aspectincludes a light guide member (1001) and a prism (1003, 1003A-1003J).The light guide member (1001) has an incident surface (1010) on whichlight is incident; and a first surface (1011) and a second surface(1012, 1012A) facing each other. The second surface (1012, 1012A) of thelight guide member (1001) is a light emergent surface. The prism (1003,1003A-1003J) is provided for the first surface (1011) and reflects,toward the second surface (1012, 1012A), the light passing inside thelight guide member (1001). The light guide member (1001) includes adirect optical path (L10), along which the light that has entered thelight guide member (1001) through the incident surface (1010) isdirectly reflected from the prism (1003, 1003A-1003J) and allowed toemerge from the second surface (1012, 1012A). At least one of the firstsurface (1011) or the second surface (1012, 1012A) includes a luminousintensity distribution control member (1014, 1014A, 1014B) to control aluminous intensity distribution of light to be extracted from the secondsurface (1012, 1012A).

According to this aspect, the luminous intensity distribution of thelight to be extracted from the second surface (1012, 1012A) of the lightguide member (1001) may be controlled by the luminous intensitydistribution control member (1014, 1014A, 1014B) provided for the lightguide member (1001). In particular, the light, passing through thedirect optical path (L10) after having been incident through theincident surface (1010) on the light guide member (1001), is reflectedonly once from the prism (1003, 1003A-1003J), without being reflected byany members other than the prism (1003, 1003A-1003J), before emergingfrom the second surface (1012, 1012A) out of the light guide member(1001). Thus, the shapes of the first surface (1011) and the secondsurface (1012, 1012A) do not contribute to guiding the light inside thelight guide member (1001). Therefore, even if the luminous intensitydistribution control member (1014, 1014A, 1014B) is provided for thelight guide member (1001), the light guiding performance of the lightguide member (1001) hardly deteriorates. Consequently, this allows thelight traveling along the direct optical path (L10) to be extractedefficiently from the second surface (1012, 1012A) out of the light guidemember (1001) while enabling the luminous intensity distribution to becontrolled, thus contributing to increasing the light extractionefficiency.

In an optical system (1100, 1100A-1100C) according to a seventy-firstaspect, which may be implemented in conjunction with the seventiethaspect, the luminous intensity distribution control member (1014, 1014A,1014B) is provided for the second surface (1012, 1012A).

According to this aspect, the light transmitted through the secondsurface (1012, 1012A) may have its luminous intensity distributionefficiently controlled by the luminous intensity distribution controlmember (1014, 1014A, 1014B).

In an optical system (1100, 1100A-1100C) according to a seventy-secondaspect, which may be implemented in conjunction with the seventieth orseventy-first aspect, the luminous intensity distribution control member(1014, 1014A, 1014B) includes a lens.

This aspect may eliminate the need to separately provide a lens sheet orother suitable optical members by imparting a lens function to theluminous intensity distribution control member (1014, 1014A, 1014B),thus cutting down the number of parts required.

In an optical system (1100, 1100A-1100C) according to a seventy-thirdaspect, which may be implemented in conjunction with the seventy-secondaspect, the luminous intensity distribution control member (1014, 1014A,1014B) includes a multi-lens configured as a group of multiple smalllenses (1141).

This aspect may eliminate the need to separately provide a multi-lenssheet or other suitable optical members by imparting a multi-lensfunction to the luminous intensity distribution control member (1014,1014A, 1014B), thus cutting down the number of parts required.

In an optical system (1100, 1100A-1100C) according to a seventy-fourthaspect, which may be implemented in conjunction with the seventy-secondaspect, the luminous intensity distribution control member (1014, 1014A,1014B) includes a Fresnel lens.

This aspect may contribute to reducing the thickness of the luminousintensity distribution control member (1014, 1014A, 1014B).

In an optical system (1100, 1100A-1100C) according to a seventy-fifthaspect, which may be implemented in conjunction with any one of theseventieth to seventy-fourth aspects, a tilt angle (θ1, θ11, θ12)defined by a reflective surface (1030) of the prism (1003, 1003A-1003J)with respect to the first surface (1011) is smaller than a maximum anglein a situation where the light incident through the incident surface(1010) is totally reflected toward the second surface (1012, 1012A)along the direct optical path (L10).

This aspect reduces, even when the angle of incidence of the light onthe reflective surface (1030) varies to some degree, the chances of theangle of incidence becoming smaller than a critical angle, thus allowingthe incident light to be totally reflected from the reflective surface(1030) more easily.

In an optical system (1100, 1100A-1100C) according to a seventy-sixthaspect, which may be implemented in conjunction with the seventy-fifthaspect, a normal to the second surface (1012, 1012A) is tilted withrespect to an optical axis of the light incident on the second surface(1012, 1012A) along the direct optical path (L10).

This aspect allows the direction of the light emerging from the secondsurface (1012, 1012A) to be adjusted.

In an optical system (1100, 1100A-1100C) according to a seventy-seventhaspect, which may be implemented in conjunction with any one of theseventieth to seventy-sixth aspects, the prism (1003, 1003A-1003J)includes a plurality of prisms (1003, 1003A-1003J) arranged side by sidein a direction in which the light is incident on the incident surface(1010). The plurality of prisms (1003, 1003A-1003J) have the same shape.

According to this aspect, the plurality of prisms (1003, 1003A-1003J)have the same shape, thus facilitating extracting the light uniformlyfrom the second surface (1012, 1012A).

In an optical system (1100, 1100A-1100C) according to a seventy-eighthaspect, which may be implemented in conjunction with any one of theseventieth to seventy-sixth aspects, the prism (1003, 1003A-1003J)includes a plurality of prisms (1003, 1003A-1003J) arranged side by sidein a direction in which the light is incident on the incident surface(1010). The plurality of prisms (1003, 1003A-1003J) includes a firstprism (1301) and a second prism (1302). The first prism (1301) and thesecond prism (1302) define mutually different tilt angles (θ1, θ11, θ12)with respect to a first surface (1011) of the reflective surface (1030).

According to this aspect, the plurality of prisms (1003, 1003A-1003J)have mutually different shapes, thus facilitating making the luminousintensity distributions of the light extracted from the second surface(1012, 1012A) different from each other.

In an optical system (1100, 1100A-1100C) according to a seventy-ninthaspect, which may be implemented in conjunction with the seventy-eighthaspect, the first surface (1011) includes a first zone (Z1) in which aplurality of first prisms (1301) are arranged and a second zone (Z3) inwhich a plurality of second prisms (1302) are arranged.

This aspect facilitates making the luminous intensity distribution ofthe light extracted from the second surface (1012, 1012A) differentbetween the first zone (Z1) and the second zone (Z3).

In an optical system (1100, 1100A-1100C) according to an eightiethaspect, which may be implemented in conjunction with the seventy-ninthaspect, the first surface (1011) further includes a hybrid zone (Z2)between the first zone (Z1) and the second zone (Z3). The hybrid zone(Z2) is a zone in which both the first prisms (1301) and the secondprisms (1302) are present in mixture.

This aspect reduces the chances of the luminous intensity distributionof the light extracted from the second surface (1012, 1012A) changingsteeply in the boundary between the first zone (Z1) and the second zone(Z3).

In an optical system (1100, 1100A-1100C) according to an eighty-firstaspect, which may be implemented in conjunction with the eightiethaspect, the hybrid zone (Z2) includes a first hybrid zone (Z21) and asecond hybrid zone (Z22). The first hybrid zone (Z21) is located closerto the first zone (Z1) with respect to a halfway line (C10) between thefirst zone (Z1) and the second zone (Z3). The second hybrid zone (Z22)is located closer to the second zone (Z3) with respect to the halfwayline (C10). In the first hybrid zone (Z21), the first prisms (1301) arearranged more densely than in the second hybrid zone (Z22).

This aspect more significantly reduces the chances of the luminousintensity distribution of the light extracted from the second surface(1012, 1012A) changing steeply in the vicinity of the boundary betweenthe first zone (Z1) and the second zone (Z3).

An illumination system (1200) according to an eighty-second aspectincludes the optical system (1100, 1100A-1100C) according to any one ofthe seventieth to eighty-first aspects and a light source (1004). Thelight source (1004) emits light to be incident on the incident surface(1010).

This aspect achieves the advantage of contributing to increasing thelight extraction efficiency.

A display system (1300) according to an eighty-third aspect includes theillumination system (1200) according to the eighty-second aspect and adisplay (1005). The display (1005) receives the light emerging from theillumination system (1200) and displays an image thereon.

This aspect achieves the advantage of contributing to increasing thelight extraction efficiency.

A moving vehicle (B1) according to an eighty-fourth aspect includes thedisplay system (1300) according to the eighty-third aspect and a movingvehicle body (B11) to be equipped with the display system (1300).

This aspect achieves the advantage of contributing to increasing thelight extraction efficiency.

Note that the constituent elements according to the seventy-first toeighty-first aspects are not essential constituent elements for theoptical system (1100, 1100A-1100C) but may be omitted as appropriate.

While the foregoing has described what are considered to be the bestmode and/or other examples, it is understood that various modificationsmay be made therein and that the subject matter disclosed herein may beimplemented in various forms and examples, and that they may be appliedin numerous applications, only some of which have been described herein.It is intended by the following claims to claim any and allmodifications and variations that fall within the true scope of thepresent teachings.

1. An optical system comprising: a light guide member having: anincident surface on which light is incident; and a first surface and asecond surface facing each other, the second surface being a lightemergent surface; and a prism provided for the first surface andconfigured to reflect, toward the second surface, the light passinginside the light guide member, the light guide member including a directoptical path, along which the light that has entered the light guidemember through the incident surface is directly reflected from the prismand allowed to emerge from the second surface.
 2. The optical system ofclaim 1, wherein the direct optical path includes an optical path oflight to be totally reflected from the prism.
 3. The optical system ofclaim 1, further comprising a light control member configured tocondense light traveling toward the incident surface and directcondensed light toward the incident surface, wherein the light controlmember is integrated with the light guide member.
 4. The optical systemof claim 1, wherein the first surface and the second surface are tiltedwith respect to each other.
 5. The optical system of claim 1, whereinthe light guide member further includes an indirect optical path, alongwhich the light that has entered the light guide member through theincident surface is once reflected from the second surface, reflectedagain from the prism, and then allowed to emerge from the secondsurface.
 6. The optical system of claim 1, wherein the prism includes aplurality of prisms arranged side by side in a direction in which thelight is incident on the incident surface.
 7. The optical system ofclaim 1, wherein the prism is tilted at least partially with respect tothe incident surface when viewed in a direction in which the firstsurface and the second surface are arranged.
 8. The optical system ofclaim 1, wherein the prism includes a plurality of small prisms dividedto be spaced apart from each other.
 9. The optical system of claim 8,wherein two or more of the plurality of small prisms are arranged sideby side to draw a curve when viewed in a direction in which the firstsurface and the second surface are arranged.
 10. The optical system ofclaim 1, wherein an optical axis of the light incident through theincident surface is tilted with respect to the first surface such that agap distance between the optical axis and the first surface narrows as adistance from the incident surface increases.
 11. The optical system ofclaim 10, further comprising a light control member located between alight source and the incident surface and configured to control lightthat has been emitted from the light source and is going to be incidenton the incident surface.
 12. The optical system of claim 11, wherein thelight control member has a function of substantially collimating thelight emitted from the light source into parallel rays.
 13. The opticalsystem of claim 11, wherein the light control member is integrated withthe light guide member, and the light control member includes a pathgenerating portion extending along a line tilted with respect to thefirst surface when viewed from the incident surface and configured toform a path for the light between the light source and the incidentsurface.
 14. The optical system of claim 1, wherein at least one of thefirst surface or the second surface includes a luminous intensitydistribution control member configured to control a luminous intensitydistribution of light to be extracted from the second surface.
 15. Theoptical system of claim 14, wherein the luminous intensity distributioncontrol member is provided for the second surface.
 16. The opticalsystem of claim 14, wherein the luminous intensity distribution controlmember includes a lens.
 17. The optical system of claim 16, wherein theluminous intensity distribution control member includes a multi-lensconfigured as a group of multiple small lenses.
 18. The optical systemof claim 16, wherein the luminous intensity distribution control memberincludes a Fresnel lens.
 19. The optical system of claim 1, furthercomprising a light control member located between a light source and theincident surface and configured to control light that has been emittedfrom the light source and is going to be incident on the incidentsurface, wherein the light control member has a shape transformationfunction of transforming a shape projected onto a projection plane,provided parallel to the incident surface, from a first shape of thelight emitted from the light source into a second shape of the lightthat is going to be incident on the incident surface.
 20. The opticalsystem of claim 19, wherein a circumcircle of the second shape is largerthan a circumcircle of the first shape.
 21. The optical system of claim19, wherein the second shape is formed by adding at least one cornerportion to the first shape such that the first shape is made closer to apolygonal shape.
 22. The optical system of claim 19, wherein the lightcontrol member has a plurality of lens surfaces on a counter surfacethereof facing the light source.
 23. The optical system of claim 1,further comprising a light control member located between a light sourceand the incident surface and configured to control light that has beenemitted from the light source and is going to be incident on theincident surface, wherein the light control member includes an incidentlens and an outlet portion and is configured to allow the light that hasbeen incident on the incident lens from the light source to go out ofthe light control member from the outlet portion, the incident lens has:a main incident surface arranged to face the light source; and anauxiliary incident surface arranged to face toward a normal to the mainincident surface and located at least partially along a circumference ofthe main incident surface, and an optical axis of the light source istilted with respect to the normal to the main incident surface.
 24. Theoptical system of claim 23, wherein light rays that have been incidenton the incident lens from the light source include a principal ray and afirst auxiliary ray and a second auxiliary ray, both of which have alower intensity than the principal ray, and the principal ray, the firstauxiliary ray, and the second auxiliary ray are arranged in this orderin a direction perpendicular to a normal to the main incident surface.25. The optical system of claim 24, wherein an intensity of theprincipal ray is a maximum intensity among the light rays that have beenincident on the incident lens from the light source.
 26. An illuminationsystem comprising: the optical system of claim 1; and a light sourceconfigured to emit light toward the incident surface.
 27. A displaysystem comprising: the illumination system of claim 26; and a displayconfigured to receive the light emerging from the illumination systemand display an image thereon.
 28. A moving vehicle comprising: thedisplay system of claim 27; and a moving vehicle body to be equippedwith the display system.